When picking a board you can usually take off the maximum and minimum sail size reccomendations as being practical to use. You can use them, but its not very efficient and will feel not so good. They are there in my opinion if you decide to have only one board. Most windsurfers discover 2 boards are the minimum, although a few of my mates like 7.
Your Carve 145, in Futura sizing would be equivalent to a F133. I suggest you keep your carve. IMHO sail size determines board size and with a 8.5 as your biggest you will need one of those 2 boards.
As your second board, I would reccomend the F101. It will take the 7.0 nicely, and will be great with a 6.5 and 5.5m. Once you become used to the F101, then the step to your F2 will be easier.
Having your 7m rigged with the Carve and F01, will give you a great wind range without rigging another sail!
The F2 is a great high wind, rough water option for you with sails 5.5 and less.
Also if your extremely happy with a board, dont sell it! A lot of people make the mistake of selling something they like, to find the replacement is a let down. Sounds to me like the Carve is helping you progress quickly, so keep it up.
I'm sure you will really like the F101.
Isonic 97 2013
JP Speed 50 2014
Severne Reflex 4 7.0,6.2,5.6