Well, Priscilla, I'll try to address all your questions in one response.
It appears Interval International provided you with their equivalent of RCI's bonus weeks. The AC in II is about the same as an RCI bonus week. There is some differences though. The AC is generally for off season inventory at a graduating price scale for Studio, 1BR, & 2BR with a specific expiration. The RCI bonus is for limited inventory, not just off season, at a fixed exchange fee.
The extra vacation/bonus weeks come from Vacation Village and are deposited in RCI. Since you made you deposit with II I'm not sure Vacation Village would deposit bonus weeks in RCI for you. But, it can't hurt to ask.
The way to do it is to call Customer Service at your home resort and make the request. At the very least when you call your home resort to deposit next year's weeks in RCI you can also ask about the bonus weeks.
TPUs work a lot like points. It's just the scale is different. However, Weeks accounts can only see other Weeks deposited by other members and developers. While Points accounts can see Points inventory AND Weeks inventory. And, yes, there's an enormous amount of information to absorb.
If you're going to do that I'd suggest you look at the low end since you already have the 4 bedroom at Williamsburg. Something like a 1BR biennial or triennial at Grandview. This will give you entry into the points world while limiting your maintenance fee costs by spreading it across multiple years.