Hello everybody

I've been studying English for my exam tomorrow , and I have a few questions please.

1- the people from next door are very noisy , I wish they .........dancing and singing.
a.to stop b.have stopped c.will stop d.would stop
I know It's not a or b , I think it's d (would stop ) , am I right or what ?
2-as he ...... , I couldn't ask him anything
what is the correct answer (had already left , or have already left ) ??
3-the doctor whom i went to has a big clinic . is this sentence correct ?
4- I will do it myself ------------ask him to do it.
a.than b. instead of c. rather than d. in place of
what is the correct answer , for me I think the sentence will be wrong no matter what I choose , cause I think that it should be asking not ask ?
5-I would have called the police if I ..........................the accident.
a.would see
b.had seen
c.saw
d. see
I think it's b , but I'm not sure , If it's b , why can't we just say saw the accident ?
thanks in advance guys.