I get it, this is very similar to something I just did but I used SPI and the boards are very close.
I had a browse at the code, but at over 3000 lines it's a bit much to absorb just for curiosity's sake.
There has to be a better way than sending stuff 3 times though. i2c slaves are supposed to be able to stretch the clock to slow things down, can you do that? Slow == reliable.
For that matter use SPI, you can run that as slow as you like.
Rob