Good questions.

Any impeachment basis specific to this is indeed murky, and since the Senate just set a precedent that impeachment requires an actual crime, get ready for "malignant incompetence is not a crime!". Personally, I would say this is "legit treasonous". Before 2020, impeachment was generally considered a political process, unwed to requiring proof of criminal wrongdoing, so long as the House and Senate agreed to remove the president. But with Bolton's latest book, it's clear that there are enough wrongdoings to merit several more investigations. It's a torrent, and it'll be tough to prioritize. IMHO, House dems should initiate these investigations ASAP, and push forwards, regardless of whatever happens in November. Everyone knows damn well that they'll never get Bolton under oath before the election, as Trump will claim executive privilege to block Bolton from testifying, and then use the courts to tie things up for god knows how long. Trump abuses the judiciary possibly more than he does Congress. Edit: of course, McConnell & co. are vvvvvveryyyyyy complicit in the judicial-packing-while-abdicating-legislation scheme.

Most of the Western world does largely seem to have given up on Syria, yes. I'm not an expert on Syria, but the continuing pattern of Putin-friendly Trump policies is unmistakable. There's no way that Trump wasn't briefed on a hostile foreign power hiring Afghan mercenaries to kill American troops. God knows what he did to avoid taking action on this. Hanlon's razor looks less and less likely.

Stay safe.