Would it be appropriate to ask our landlord for money off of our rent this month?

Look through your lease. There might be a clause that forces him to give you compensation for that. Otherwise, this is a business transaction and you have every right to ask. If you're good tenants, he should want to comply, because you CAN move elsewhere when your lease is up and he could get stuck with a terrible tenant. Just know what your options are and be clear about what you want and why.

Yes.

In CA, you have a right to withold rent until agreed-upon repairs are done. In the case of a sink, toilet, leaky roof, Yes. (Maybe not an addition).

The landlord will sue for the rent, it will go to court. You can then show pictures, bring whatever documents stating when he agreed and so it's now so long you've been without the sink; receipts, etc. The judge will decide if landlord gets his rent or not, and, the possibility of you getting pain and suffering money as well as recompense for the paper plates, spoiled food, fly paper, etc.

I think absolutely as a tenant you have the right to a well maintained dwelling as a landlord they are responsible for maintaining it. Look at it this way if you failed to up hold your end of the deal would they hesitate to ask you to leave..... As to the amount I would guess the amount you spent on paperware and spoiled food

Probably better to file a complaint with the rental agency commission if your City. Call your city government help line and ask for the name of the agency and how to make contact.

won't hurt to ask, he can only say no, i'd say maybe $100 credit would be ok.