In the book the "bet" had a different viewpoint. Through meditation he found something inside him draining his magic power constantly (which is why he was in a coma for so long) and noticed that he could store a bit of extra MP in the mark he shares with roseweiss. He's able to use the mana stored to absolutely destroy her in their bed games, but it's zero sum, he loses what he saves because of her honry. His idea of getting a month off is basically, "Oh man I can stockpile a shit ton of MP and REALLY bring the hurt to her (in bed)"
The mark does a lot more than share their feelings/desire and there's a REASON it was prohibited.
Also...when they get 2 marks the wheels come completely off.
So him being "a wimp" here was actually part of a strategy to ensure full future bedroom domination.
Also, she notices that he's regaining power (but not the how) which is why she's escalating. She knows that if she doesn't drain his batteries on the regular, she's going to end up being his pet. Dragon pride. Of course, her trying to use the curse to dominate him backfires in a big way.