Ah, sorry OP, I just saw your updates.
I'd be really pissed off. He goes on and on about how much he wanted to get married with his ex wife and the tens of thousands he spent on her ring.
Then tells you, he doesn't want to get married, but sort of will now out of acknowledgement to how you've stuck by him. So just use a ring you've already got.
That's not ok. He's saying, look how I treat someone I do want to marry, now see how I treat you.
He's doing it because he thinks you'll be off if he doesn't. Not because he wants too. So you should be accepting of the zero effort, bargain basement treatment, because you should be happy that he's graced you with a marriage at all.
Out of interest, is your 40th ring, a "tens of thousands" ring, as in, he thinks you've got "the ring" already, from a time when marriage wasn't on the cards for him. Now it is on the cards, he thinks of it as the important ring?
If it's more of a token/costume ring, then he's being a dick trying to take it back to reuse as an engagement ring. Because clearly he can buy a proper one for someone he wants too.