I had kind of similar experience at Coronation few weeks ago - broke the mast a fair way out but luckily did not get hurt.
I did not try to waterstart as it did not seem feasible to lift the rig out of the water. I considered de rigging but thought it was likely the rig would sink. I decided to swim it back to the beach, which took me about 45 minutes. It was nearly dark by the time I got back. Luckily there was a German kiter out there who kept an eye out on me and even tried to pull me to the beach (very hard as it pushed my head under water whilst hanging on his harness with one hand and on to my rig with the other

). But thanks mate, it was great to know someone knew I was out there (my friends only spotted my board upside down when I was nearly back).
Anyone has any tips on getting back with broken mast (just above the boom)? The only thing that comes to mind is to ditch the rig (or try to salvage what you can) and paddle back on the board.
With regards gybing in the swell: I had/have the same problem, I can nail my gybes in safety bay and even between the waves at Coronation, however the succes ratio falls when in the swell.
I think my problem was standing too far back on the board, which made me loose lot more speed and the board stalls half way through the turn. This is easier to overcome on flat water than in the swell.
I think it might also be a mental factor as I do feel bit scared (little voice in my head saying: "oh no, I'm not gonna make this one and I hate water starting in the swell where the water is dark!!!"

).
So I stand back (seems safer, further away from the water - right

- where is the logic in that



) and the board stalls, and I loose balance when the next wave comes.

Moving weight forward, sheeting in harder, bending in the knees made a huge difference on flat water (faster gybes, carving through the turn, still planning on exit).
I also look for a flat bit of water or use a face of wave to give me extra bit of speed and remind myself to move forward not to stall the board. Also remember if you move forward you will stand over the the board where the volume is, so more balance if you loose speed.
And above all: Full commitment!!!
Cheers