seems like you weren't "so sweet" to him as you think . you were polite... you both enjoyed sex. but he was actually thinking about whether reconciliation with you would be worthwhile. whether you would treat him better than you did.
the answer seems to be "probably not". that's sad so, for him, you are at least nice enough for an FWB situation... but not to be married to.
I think a lot of people would expect their spouse to do for them what he asked of you, FYI
