-He has overlap so he has luffing rights (R11).

-If he luffed too hard he would be in breach of R16.1 (when RoW boat changes course, she shall give the other boat room to keep clear).

-If he started luffing just after the overlap had been established he also would have had to keep clear (R15).

-Had you capsized you could have maybe protested for R2 (fair sailing), but not easy to prove.

If you filed the protest I think R11+R16.1 would have the best chance of success (especially since he went from a downwind to an upwind course).

I highly recommend taking a look at the ISAF Case Book, it describes all sorts of situations and explains the reasoning behind it:
http://www.sailing.org/tools/documents/CaseBook20092012with2010changes-%5B8229%5D.pdf