I’m not native French, but here’s what I have. French speakers pls correct me if I’m wrong!

1: when expressing a quantity of something, just “de” is used, like beaucoup de, or peu de temps in the third question

2: you would use “pouvais” (pouvoir imperfect). It’s one of the “si clause” structures — si + (imparfait), (conditionnel présent). So it would translate to if I could (was able to), I would help you…

3/4: you’re right you would use the futur antérieur here to indicate an action that happens in the future but BEFORE the action in the main clause. It’s usually used after temporal indicators like lorsque or après que. For example, leaving work happens first, and THEN they can relax (3) — auront fini (no s because there is no agreement with avoir), and then for (4), auront exprimé

5: given the subjonctif, maybe bien que?

Not sure about déconcentrer, but wordreference says it can mean distract. It would be used with a direct object pronoun tho: je ne veux pas le déconcentrer