Not if you don’t leave the airport (I think) but check with airline as they might have more up to date info. Restrictions have been relaxed in CNX recently
I thought you had to show proof of fully paid first month at least but, if you don't, or you can arrange to get refund of that, I don't see why not, as long as you log a new TM30.
In country, you need to have funds in a Thai bank account 2 months prior to applying, and it can be quite difficult to open one and then 'season' the funds in that amount of time (if you don't have account already). This is true even if you get an extension (which the poster above's email would suggest you cannot), what with quarantine etc. You might be better off getting retirement visa in your home country, if available, because then the funds only need to be seasoned in your own bank account.
I know about the criticism of the Embassy (as always). When you say 'here' .. I live in Thailand too. TBH You don't know the way they prioritize their work. 'I am sure' really counts for FA.
Not really. The Embassy has a duty of care for its foreign nationals irrespective of why they are in a country. You won't be treated differently from anyone else (and this is not to say they will give you a huge amount of support, just the same as to anyone else).