I agree, make sure you look upwind all the time to spot gusts and lulls so they don't hit you unexpectantly. If I know I am going to fall backwards, I usually just sharply pull the boom towards me and I unhook. that way I can land in the water and really extend my arms to keep the sail flying. Saves a lot of work recovering the rig.
When I know a lull is coming, I bring my hands closer together to get myself further away from the rig, and lift the hips while pushing the boom away. this action brings you more over the board and won't result in a splash if done correctly and in anticipation for a lull.
If you are underwater with the sail ontop of you and you are hooked in, try tapping the boom 3 times to ease some of the panic away from the situation. After that, calmly move your hands towards the lines and raise your hips towards the boom and manually unhook the lines with your hands. After that, blow out through your nose so water doesn't come in and you are ready to resurface. ahahah just remember not to kick the fin