He wants to make her suffer for leaving him, I think. He said it before that he wants to have her in as much pain as he was in when she left, which is why he took advantage of the fact that she had amnesia to mess with her instead of….idk, leaving her be? Ig we wouldn’t have this story if he was sane lol.
Keeping her as a maid would give him more power over her, and more opportunities to torment her, so he’d basically be able to do anything he wanted because she is “beneath” him in social status. Bro needs to get a hobby

Question, so does he know she's his wife or not?