Proton wouldn't have to disclose the real IP from anyone using their VPN, you can read their Blog-Post on that here. I think they fixed the next point, but why wouldn't it redirect to a clearnet site? You are already using tor, hopefully on the "Most Secure" setting, so why would you care? VPNs can be secure (like proton or, even better, mullvad), but I agree that most of them aren't. I also agree that E-Mail was not designed to be secure, but that doesn't mean that it can't be. PGP exists, and since proton is heavily pushing for you to use it, I think it's okay to use their service.

Cock.li is a nice Mail provider with a not so nice owner and while the philosophy behind it is pretty cool it's AFAIK also on every spamlist possible. Also the domains are, aside from airmail.cc, just not good for any professional usecase