Hi jass,
Wow, sounds like you're going to spend a bomb! Anyway, just my 2 cents worth.
1) You can always start preparing as soon as you can. Book the venue (church) and priest first if they allow such early bookings.
2) Ask your priest if he's "providing" the altar boys. Oh yah, that reminds me that I have to ask my priest about the altar boys too.
3) I don't think it really matters that they have to be single. After all, I feel that bestman & bridesmaid are basically your good friends who are going to help you on the AD. But I AM a bit of a "rebel" where these "traditions" are concerned.
4) Discuss this with them but normally, yes, you pay for their suit/gown.
5) I'm going to only have 1 pageboy and 1 flowergirl. And yes, normally you do have to pay for their clothes. Unless you're really close to their parents and their parents insist on paying their ways.
6) You can try Delihub for catering. My office often uses them and the food is not bad.