RE: whitch board
When it comes down to the right volume, it's important to ask yourself whether your waterstarting skills are fairly strong. If they aren't, and you must depend on uphauling, then some extra float will needed.
You indicated above that it is essential that the board float you in 3 knots. That is very little wind, but if you are talking about motoring in or out from a distant windline, that quite possible with a smaller (less than 100 liters) board. Really, when it comes to low volume boards, there is always a chance that the wind will die and leave you with a possible swim. So you have to consider this if you decide on a board under 100 liters.
Given your sailing goals above, it's my thought that the Kombat line is your best bet. As a crossover type board, it will do it all, including an opportunity to ride small waves too. The Carve line would be a good choice too, but I believe that freestyle really isn't its strongest suit. Unless you really want to concentrate on freestyle moves most of the time, it might be better to go more allround in your emphasis and overlook the Flare for now.
Regardless of your board choice, you need to consider whether you are prepared to take some risks regarding the amount of volume you need. Also, you must consider the sails sizes that you anticipate using, as that will help you focus a little closer on the proper board size.