A couple points:
Firstly I think it is much more likely Ukraine would declare neutrality than give up Crimea, the DPR and the LPR. Ukraine knows they're nowhere close to joining NATO anyway, and if neutrality means security guarantees, why would you not agree to that at this point? Crimea, LPR and DPR are a matter of Ukrainian sovereignty however, I see no room to cave on that.
Secondly, I would not trust Putin's words at all. Ukraine was given security guarantees for denuclearization, look where that got them. Likewise, Russia decided, on their own accord, to tear up the Minsk agreement under completely false pretexts. What's to prevent them from doing that again. Additionally, Russia can't even adhere to humanitarian corridors and is bombing apartments, nuclear power plants, and assaulting hospitals. I would not for a minute trust this mans word, not to mention his clear desire for regime change, and his failure to acknowledge Ukraine as a country, nothing stops him from slowly chipping away again and again.
Disagree. This goes back to 2007 where Putin basically put NATO on watch. Since then he's invaded Georgia, the Crimean Peninsula, and also turned Belarus into a Russian vassal state while also propping up the DPR, LPR and Kazakhstan (which he also recently declared didn't deserve statehood very similar to Ukraine)
He's also publicly stated he wants NATO to roll the clock back to 1997, this was literally one of his demands in negotiations with the West leading up to the invasion. This, among other things, means no baltics or Poland in NATO. Additionally he's talked about how the fall of the Soviet Union and the Russian Empire are among the world's greatest tragedies. So to suggest his conquest ends at Ukraine is folly in my opinion.
Just look to his recent summit with Xi and Putin, where they outlined their partnership for what they called a "new era" and their desire to create a more democratic globe, respect for human rights etc. China and Russia have incredible ambition, and want to topple western hegemony. At the very least if Putin is going down, there's no reason for him to not try and drag the West down with him.