The Futura 101 certainly will carry those sail sizes and I would say the sweet spot really is around 6.5. I've used the F101 with a no cam slalom sail in 7,5 and a cam slalom sail in 6.6 and I would say cam slalom 7.5 would work great. Possibly you need a more high strung fin (either bigger or more performance oriented).
Wether its the perfect board for you or not depend more on what you're after when it comes to feel. The Futura has a lot of iSonic speed in it but it comes with a much more subtle and calmed down feel. In high wind your choppy waters the Futura requires much less balls and I would also say it requires less technique to get going early in light wind (despite actually being slower off the mark if you really go the techique to get the iS going super early). But you will also loose a bit of of end compared to an iS.
If you want a more high strung racing feel yo could also look at iS96 or even iS 86 if you're light.