I don't think it's an immediate LTB offense. But I do think that in order to move past it, he's going to have to acknowledge the situation for what it is, not just what he wants you to believe.
"In another life" is a wishful statement.
If you were looking at your favourite car that you couldn't afford, you could say "in another life, that would be my car". That's coveting.
If you hope to see somebody again but know it's unlikely, you'd say "see you in another life". That's wishful.
If you were looking at your career and thinking you'd rather be doing something you love, you'd say "in another life, I'd be working as an X"
You wouldn't say "in another life, I'd be driving to Sainsbury's", it's too dull. If you did say that, people would think you really loved Sainsbury's 
I can't think of any situation where you'd say that and not mean it's something you wish you could have had.
If he's willing to acknowledge that, to talk to you about how it obviously makes you feel and to accept that it's inappropriate, then I don't think it's worth dwelling on.
However, if he tries to minimise it by saying you're reading too much in to it, then I think you have bigger problems than you may realise.
I'm very sorry, this sounds like an awful situation to find yourself in 