He wanted to pay her back for cooking so delicious, but since he knows he can't cook as well as his wife (or for that matter cook well at all) he's inviting her to a restaurant so that he can use his money to get her something nice to eat... together (2 birds 1 stone).
They used to work together. Did she leave work after the marriage? Japan is quite patriarchal country.. Probably office work is not very fascinating, but why not work together if you don't have babies yet.
This man is so smooth... but can we give him a face and name instead of him being anyone's self-insert?
This man deserves to really be his own character.