1. Your statement is correct. You can only book at a home resort at the 11-month point with the number of points you have for that resort.
However, rather than waiting for the 7-month point, here are some suggestions.
With a 25-point contract and using banking and borrowing to the maximum extent, you can have 75 BCV points to book with every three years. Obviously, 75 points is far more flexible for booking than 25. Use your add-on points every third year and use your other, larger contract in the off years.
If you don't have enough home resort points to stay at one resort for the entire trip, the safest thing to do is book consecutive stays at both of your home resorts at the 11-month point. Then, at the 7-month point, try to switch one reservation or the other. If they have anything available, great! If not, ask to go on the waiting list. If the waiting list comes through, great! If not, you still have a room for every night of your stay; you just need to switch resorts mid-stay. (This means you need pack your bags, check out and check in an extra time, but other than that, it isn't too bad. Bell Services will even take care of getting your luggage to the new resort for you.)
2. If buying from Disney, the points all cost the same, whether you're a new member or adding on points. You'll need to ask your guide what the current incentives and discounts are. They change so often and they have so many of them it's hard to keep track.
3. This is a complex question and depends on where you were going to use your points.
If staying at a
DVC resort:
Cancel more than 30 days from check-in, your points are returned to the use year in which the reservation fell. The points have no special restrictions because of the cancellation, but are still subject to the normal banking and borrowing rules. Depending on how late your reservation was in your use year, you may not be able to bank the points because of banking deadlines. If the points used for the reservation were banked or borrowed from another year, that can't be undone and they'll have to be used in the use year in which the reservation fell.
Cancel 1 - 30 days from check-in, your points are placed in a holding account in the use year in which the trip fell. You must use the points by the end of that use year or they will be lost. You cannot book more than 60 days in advance with holding account points. Holding account points can't be banked or borrowed. You can use holding account points for the other collections, but not in the last 60 days of your use year.
Cancel on the scheduled day of arrival, your points are lost.
For the Disney Collection, Adventurer Collection, Concierge Collection, and World Passport Collection, there are different cancellation deadlines for practically every location. You can find those on the member web site.