That he is Tom Riddle.

A whole lifetime's worth of stuff, which is repressed and forgotten by Tom Riddle Jr.

The slow nanowire penetrates the shield.

Or he and Bella are kicking back on a beach in the Caribbean, drinking alcohol from coconuts and murdering anyone who plays loud music nearby or fails to clean up after their dogs.

Rematch in twenty years.

Yeah, this is one of those solutions that, had I been writing, I would have ruled as not actually workable. Takes too long, Voldemort or a Death Eater sees the threads and breaks them on general principles, nanotubes don't actually have enough tensile strength to reasonably slice up everybody at once consistently, and so forth. I pretty much filed any tactical violence plan under "not practical".

Still, not my story. It's not out of keeping with the rest of the stuff in HPMOR.

High odds that Voldemort escaped. He's been extraordinarily hammy this whole time, and he called all the Death Eaters together, killed or crippled a few, and then explained his evil scheme to the hero before giving him a countdown to his inevitable death, while leaving him armed. It seems very plausible that Tom Riddle was tired of Lord Voldemort, and decided to retire him via dramatic massacre. Why make his new body a snaky freak-show, after all?

On the pedantic nitpicker trivia side of things, you don't have a tank of "oxyacetelene". An oxy-acetylene rig uses a tank of oxygen, and a tank of acetylene. But Harry is probably not a welder, and neither are the Weasely twins, so nobody involved was equipped to notice the problem.

I don't recall invisible shields, but it's certainly plausible.

We've also seen him just flatly stop curse bolts in midair and then flick them away, without apparent shielding or obvious effort. He's got defense options like Smaug has gold coins.

If killing him was easy, someone would have done it before. Even though he had horcruxes, it's telling that he never actually had to respawn from one until he tried juggling dynamite and blew his own self up.

Wise sort of went on vacation when Harry elected to oppose the invincible dark lord instead of volunteering to be his most favored flunky.

Voldemort is capable of making stupid mistakes; he admitted that with his whole discussion of being trapped for years without a body. But he doesn't make stupid mistakes very frequently. So, if you believe he's making a stupid mistake, you should try to take advantage, because you may not see another one.

Harry has literally been watching the current body Voldemort is inhabiting for the entire time that body has existed. He has seen every spell cast while Voldemort has been using it.

Either Voldemort has not raised shields (which he typically did not do as Quirrell) or he's capable of casting shielding spells which Harry cannot detect either the casting or ongoing effects of even in the midst of extended close observation. And if it's the latter, we're back to "in order to have a shot at beating someone, you have to assume he's theoretically beatable and act accordingly".

On the gripping hand, I'd more expect his new, permanently-transfigured body to just be naturally bulletproof, rather than conventionally shielded. But it's not helpful to believe he's actually thought of everything.

Depends on the poison.

If it's something that prevents the poisoned person from noticing he has been poisoned, sure. Doesn't matter if you could fix the problem, if your brain has been prevented from realizing there IS a problem.

Alternately, if the "poison" is some sort of deleterious transfiguration effect upon the subject, which the stone will immediately make permanent, it would be hilarious. Snape, at least, thinks this way. Remember his attempt spike Voldemort's resurrection components with LSD?

You're right, I would expect the troll and unicorn merges to have caused interaction. Hmm.

Seems, then, like the resonance is more a complication of doing unusual things with the horcrux ritual than a matter of Voldemort's magic affecting Harry, per se.