That's just it, we know that there was a war and that that reality's Hulk beat a bunch of heroes. /quote]
Not exactly. The novel "What Savage Beast" and Future Imperfect pretty much stated that he holed up in the Gamma Cave (now well stocked with food, supplies, and various pieces of technological equipment) and waited for the war to be over, and the war is what led to most/all of the other super-powered people dying.
As to the silver surfer - Marvel: Zombies had a zombie Hulk bite his head off, so I imagine the much stronger Maestro could rip his head off easily.
Saint of Killers - lame as I found this, enough Gamma Radiation allowed the Maestro to reconstitute his ATOMIZED ASHES and come back from the dead. The Saint could kill him, but as show with the much weaker Grey Hulk's battle with Wolverine, he can heal in seconds. So if he dies, he comes back to life. If he gets merely wounded, he heals almost instantly. The Saint survived a nuclear blast, but the Maestro could MAYBE come up with a device to negate his heavenly abilities (eventually) and kill him.