1) I agree NATO should not expand. I agree this issue is not partisan. We can disagree on it, but I don't consider this to be a partisan issue. (Although I dare say if Trump tried to do this, he would be accused of doing it for Putin. This is what Putin wants, after all...it just also happens to be a the right move for many reasons. Just shows you how ridiculous all those accusations were.)
2) Doesn't NATO have treaty obligations to defend Ukraine?...obligations that NATO volunteered for in order to convince Ukraine to naively turn over their nukes to Russia? (Maybe not NATO, but at least the US and UK?)
That is not membership, in that there is no shared training and the like. But, it is a defense pact by at least some NATO nations, which, if war broke out, might trigger NATO action. I don't know the terms of it...just that promises were made. So, to some partial degree, it has already been done with Ukraine.