I sail a Falcon uni with the same main as you, I'm definitely a heavyweight!

A few things you could look at:

Foot setup - Make sure your foot is set up as per the Falcon guide, could be too loose and you can't flatten off enough.

Mast rotation - I find the main really sensitive to mast rotation, the sort of conditions you are talking about, you seem to have it where I normally would, but there seems to be a pretty narrow 'sweet spot' where a bit further in you lose all power and a bit further out and lose all pointing.

Batten tension - I actually have a bit of tension on the battens unless it is really blowing, but you could try a bit less.

Mainsheet - In max hull flying conditions I find I am working the main all the time - seems to be the only way to stop that hull popping effect. Use the cleat as little as possible, try and drive in a straight line and keep the hull just flying, try and anticipate the gusts or feel the pressure coming on the main.

Then again, my local lake here is very gusty and swirly, if you get hit it's almost impossible to react quick enough.