I can only help with your use year question...
It really only matters if you cancel a reservation. If you cancel a trip towards the end of your use year, you are limited in how many of those points can be "banked" into the future year. You can only bank 100% of your points in the first 6 months of your use year.
So...lets say you have a Feb. use year. You get your Feb. 2002 points and plan a trip using all of your points for Dec. 2002. But in Sept. of 2002 you learn you can't make the Dec. trip and won't be able to get to a
DVC resort until sometime in mid-2003. So, you cancel your reservation. But since you are past the 6 month window for banking all of your points, you can only bank 50% of them. The other 50% will expire on 1/31/03. You'll either have to use those points at somewhere other than DVC (and using points this way is usually a very "expensive" way to stay somewhere), rent your points to someone or give them away.
I plan on travelling a lot in Feb., Mar., and April, so I went with a Feb. use year. That way, if I have to cancel with a couple of months to go I will still have several months to bank all of my points. (Keep in mind that cancelling with a month or less has its own headaches.)
Hope this helps.