Unforgettable- If I were you I would keep the Kombat 112, because at 85 kg, a 102 would not be enough security for "byebye" wind. To make it more comfortable in strong wind and rough water, I would experiment with different tuning, like adding extra downhaul to the sail, adjusting the footstrap widths and positions, and trying short, low-aspect ratio fins that will calm the board down but won't spin out.
Examples of fins that might work well:
If that doesn't work, you might think about getting a board between the 80 Evo and the 112 Kombat. Maybe a 90 Evo. Even though it would still be too small to uphaul, you could begin to use it in lighter winds and with the 5.8.