mana-āyatana is 7 viññāṇa-dhātu (7 mana-āyatana) that is dvāra of mano-viññāṇa

In tipitaka of theravāda-buddhism, viññāṇa in mano-dvāra are called thinking.
Viññāṇa generally translated as "consciousness" in english-tradition. This is a terrible translation, because when we compare viññāṇa with english in sense article, viññāṇa is not just the consciousness, but consciousness is the part of viññāṇa. There seem to be:

1. Six viññāṇa, such as seeing, etc. = Six sense, not just consciousness, however consciousness is included in the part of sixth viññāṇa, too.
2. Six dvāra, such as eye, etc. = Six sense-organ.
3. Six object, such as color, etc. = Six sense-data.

The sixth dvāra called mano, that is enumerated to 7 viññāṇa/mano in 18 dhātu, such as cakkhu-viññāṇa/mano, etc. for describe mano in 12 āyatna. A cakkhu-viññāṇa arises at eye-dvāra to see a color-object. But when mano-viññāṇa will arise to think about that color-object, which was saw by that vanished cakkhu-viññāṇa, mano-viññāṇa will not arise at the eye-dvāra. Because the dvāra of mano-viññāṇa is not the cakkhu-dvāra, but the pāli said that mano is dvāra of mano-viññāṇa. So, when mano-viññāṇa thinking about a color-object, it thinking at cakkhu-mano, cakkhu-viññāṇa. So, first viññāṇa at mano-dvāra is called mano-dvāra-āvajjana. And so, mano-viññāṇa is called "mano"-viññāṇa. Therefore, Mano-viññāna is a thinking about a saw color, a heard sound, a smelled smell, a tasted taste, a touched touching, and a thought thinking.
So, in abhidhamma said that mano, viññāṇa, manoviññāṇa are the synonym. But they are used by buddha in difference function in each pali context, for avoiding the confusion of homograph and for briefing the word, such as 7 viññāna-āyatana brief to mano-āyatana, to make new word "mano-viññāṇa-dhātu", buddha is very intelligence!
Another, there is someone maybe teach consciousness is not thinking, because he has a weak pāli skill and never listen anyone around him. Especially, he never recite tipitaka, follow buddha's order, in A.N. Pañcakanipāta, to recite the teaching. This case often happen with the western professor, because they have a superego in their mind, so they always close their ear and their mind to learn the others' views. So, he never notice this pali's relationship. And he just always told that consciousness is not thinking, although consciousness is one part of mano-viññāna.
However, this case also happen to thai tipitaka translation, too. So, I often remind everyone to recite tipitaka in pāli, especially before teaching something. Especially when you listening the translate version of tipitaka, especially, from the western professor.

Meditation's Effect on Strong Attachment

I have a straightforwards question: does meditation decrease attachments -- e.g. to alcohol or social media -- by increasing willpower, or by other mechanisms? I would think shamatha increases willpower in the long-term, but does it produce some other effects that decrease attachments?

When you concentrate out of alcohol, you are not attaching alcohol that time. The distance between you and alcohol will increase. This can be meditation, if your concentration concentrating samādhi object or vipassanā object continuously and improvely. But, if not, it is just a sīla, precept, if you just deny to drink an alcohol, because alcohol denying is just a precept in 5 precepts, so it is just meditation base, but it still not meditation.
Sīla-training stop whole physical attachment, not just alcohol. Sīla is base of meditation, but it is not meditation because mental attachment still able to arise. When any unwholesome mind, such as attaching mind arising, that time is not meditation, because the meditation is training continuously and improvely.
Samādhi-continuous-training stop whole present mental attachment.
Vipassanā-continuous-training extirpate whole future attachment.

Balancing the Five Powers

It is too easy to understand, but it is very hard to done.

The example in concentration meditation:

1. If you have too much trust to concentrate on focus, you will over hurry to sit and to meditate. That hurrying maybe make you miss to concern, smart & wisdom, the meditation's situation and environment, such as it maybe too hot temperature to develop concentration meditation. So, your meditation will not grow up.
2. If you have too much effort, you will too much concern the meditation's situation and environment, then you loss the meditation's focus. So, your meditation will not grow up.
3. If you have too much concentration on focus when you still being bore, you will sleepy. But you will not decide to stand up and go to do caṅkama, walk meditate, to avoid sleepy. Because you miss to concern, smart & wisdom, the meditation's situation and environment. So, your meditation will not grow up.
4. If you have too much smart and wisdom, you will too much concern the meditation's situation and environment, then you loss the meditation's focus. So, your meditation will not grow up.

Etc.

For more information, I recommend you read whole of path of purification especially in pathavīkasiṇa-niddesa and in maggāmaggañāṇadassaṇavisuddhi-niddesa. There are many explanation and many tools for the balancing inside there, such as 7 sappāya, 10 appanākosala, etc.

The last giving in Dana Mahapphala Sutta

Dana Sutta:

" — but with the thought, 'This is an ornament for the mind, a support for the mind' — on the break-up of the body, after death, he reappears in the company of Brahma's Retinue. Then, having exhausted that action, that power, that status, that sovereignty, he is a non-returner. He does not come back to this world.

At the end of sutta, said that the last dāna-method, your quote, is dāna of anāgāmi-ariya:

with the body’s breaking up, after death, he reappears in the company of Brahma’s Retinue. Then, having exhausted that karma, that power, that status, that sovereignty, he is a non-returner. He does not come back to this world.

So, in this sutta's commentary said:

"an adornment for the mind, a support for the mind" means a support for concentration-meditation-mind and insight-meditation-mind.

Because, anāgāmi-ariya completely & perfectly escaped five strands of sensuality, kāma-attachment, so his attachment in his gift can't arise anymore, too, because gift is five strands. So, dāna in the last method are the best, because it is giving as alike as anāgāmi-ariya's and arahanta-ariya's giving. These two ariya just give for meditation, mind development.

To understand tipitaka deeply, reciting & memorizing tipitaka are strongly required.

Priority of Meditation

Bad physical habits are stopped by adhi-sīla, physical observe.

Then, bad mental habits are stopped by adhi-samādhi, concentration-meditation.

Then, whole, future, bad habit's root-causes, avijjā-root & taṇhā-root & dosa-root, are vanished by adhi-paññā, insight-meditation.

No one can avoid any kamma in a very long travel in saṅsāravaṭṭa

No one can avoid any kamma in a very long travel in saṅsāravaṭṭa, except niyata-bodhisatta (bodhisatta who has enough experience to be an inevitable person to enlighten as buddha).

However, niyata-bodhisatta still born in hell, except just avīci-hell, still born as animals, except just very small and very big body animals, etc.

So, although you are bodhisatta, you still can not avoid the hell.

In commentary's statistic, just jhāna people have a lifetime much enough to get a very small chance to meet metteyya-buddha, and just 4th jhāna people (of 8 jhāna) and anāgāmi-ariya have a lifetime much enough to get a very small chance to meet next buddha after metteyya-buddha.

The other people, such as all 1st-6th heaven people and all human, will die before the next buddha meeting, and their death can lead them to the hell infinity time, before their next buddha meeting.

Bodhisatta develop their wholesome minds without any fear, although they realizing that they will born in hell uncountable time before the enlightenment.

What is the difference between Dhithi (view) and Panna (wisdom)?

Right, Sammā = possible to happen in reality cause and effect rules.
Wrong, Sammā = impossible to happen in reality cause and effect rules.
Diṭṭhi = attitude element of mind that collecting several right/wrong aspects of knowledge.
Paññā = learning element of mind that learning several right/wrong aspects of knowledge.
When you learning knowledge, is while you collecting knowledge. 
So, Diṭṭhi = Paññā.
Therefore, SammāDiṭṭhi = the attitude element of mind  that is right, possible to happen in cause and effect rules, such as paṭiccasamuppāda, paṭṭhāna, or 10 sammādiṭṭhi, etc. = SammapPaññā = The learning element of mind that is learning several aspects of learning knowledge, that is right, possible to happen in cause and effect rules, such as paṭiccasamuppāda, paṭṭhāna, or 10 sammādiṭṭhi, etc.
See: abhidhamma such as ñāṇavibhaṅga, and understanding chapter of part of purification.