wwall: If 27...Nxa3, then 28.Rc7+ Rd7 29.Rxd7+ Kxd7 30.Bd3 Ke7 31.h4 and White is slightly better.Instead of 28...Nd2, perhaps better is 28...Qd6 29.Ba2 Rg8+. Weaker is 28...Nxa3 29.Rd6 Qa7 30.Ba2, threatening 31.Re6+! fxe6 32.Qh7+ and 33.Qxa7.
Instead of 29...Nc4, perhaps better is 29...Qe6 0.Rc7+ Kd6.
Instead of 30.Rc3, 30.Ba2 looks stronger. If 30...Nx3, then 31.Qxh7 is good for White.
31...Qd8 looks weak. Perhaps best is 31...Rd2, threatening 32...Nxe3+! 33.Rxe3 Qxe3, threatening mate.
Instead of 34...Qb6, perhaps best is 35.Ne8, threatening 36.Rxd3.
36...Ke6 looks like the losing move. Perhaps best is 36...e4 37.Rc5 exf3+ 38.Kg1 Rd1 and Black might hold.
After 37. Rc5, White threatens 38.Rxe5. If 37...f6, then 38.Rc7 wins.