1. I don't approve of what you are both doing, but I'm not going to berate you, otherwise the question becomes rather pointless.
Assuming that you are going to carry on, and that you want non-judgmental replies, then ...
2. Obviously, what you give to him is a no strings relationship, and (presumably) something sexual that he is not getting at home. This frequently involves dressing up (as you say), and the freedom to do things without feeling awkward at the breakfast table the next day ... oral sex, new positions, or whatever.
Unfortunately, that is the conventional lot of the "other woman"
As I've said ... I'm not judging you here.
The bottom line is, we have no control over who we fall in love with.
Whatever you both do, I hope things work out with nobody getting hurt.
JJ x