AITAH for not paying the lease break fee?

I (24F) moved in with my fiance (26M) 2 years ago. I am a stay at home mom, upon him insisting that I don't need to work anymore. We are both on the lease. Yesterday, I get a dm from a friend of his, saying he's been cheating on me for almost the entirety of the last two years.

We have been together for 6 years and I never imagined this would happen. She had proof. Images, videos of him, mostly pda, with some other girl. She explained that she found out a month ago and has been debating telling me as we have gotten quite close.

I confronted him, and long story short kicked him out. The landlord said that if we did not live together anymore, we would have to pay the lease break fee, which I have no means of doing. He's refusing to pay because I'm the one who kicked him out.

WIBTAH for taking legal action to get him to cover the fee or is it my responsibility given that I am the one who kicked him out?