You are clearly underpowered at 101 kg (I proudly carry teh same weight myself) with a 7.5 m2 sail. For me a 7 m2 sail is the largest sail I use on my smaller 106 liter board, and the wind really needs to be 20 knots or more.
When it is less I prefer to rig a 9m2 sail on a 135 liter board. Only then will you get a sufficient number of planing days. This is particularly true if you are an intermediate and not yet a specialist in effective pumping and early planing.
The difference in power between a 7.5 and a 9.0 is considerable! Thus, keep the board, get yourself a bigger sail and you will get a lot more planing days. You may also then want a bigger fin with around 46 cm of length for the lighter days.