No, NATO is absolutely the redline and even the smallest nato baltic countries usually have allied troops stationed there. To think NATO wouldn't defend a member state is completely unrealistic and that's one of the reasons this entire conflict started. If ukraine joins NATO it becomes untouchable, even for putin, hence why they were willing to support the donbass rebels and escalate to a war now. If putin was just going for the easiest target and didn't mind NATO, ukraine is hardly the weakest target in the area.
Once you attack a NATO member you are almost automatically at war with all the members of the alliance and you'll probably have to face already present nato troops as soon as the war starts.
I understand the theory of what you are saying, NATO as an alliance is focused around the "red line". However, in practise, will the US/UK/etc risk a nuclear war over Montenegro? Even today, with Biden and Boris in command, the answer in not clear. With a potential future anti-NATO Commander in Chief there is even more doubt.
This is the theory, but let's be honest: will Western politicians really risk a direct armed confrontation with Russia - when the latter almost openly threatens to escalate (hinting at WMD) if anyone intervenes - over, say, Latvia?
Actually, that's not the right question, because Europe by itself doesn't have the military strength to escalate. So it'll be down to American politicians and American voters.
Yes, because he was still very actively supporting the countries bordering russia. He didn't like the structure of NATO but that's mostly because he wanted more involvememt from European countries, not less. I don't think any president would actually back off a nato member getting attacked.
Once you attack a NATO member you are almost automatically at war with all the members of the alliance and you'll probably have to face already present nato troops as soon as the war starts.