Yeah ok buddy, whatever narrative helps you feel better about getting your dick wet while you help someone hurt the person they supposedly care about.
If they need out help them get out instead of selfishly giving them an escape that doesn't actually help them escape and actually makes things worse. You aren't breaking the chains, you are helping her keep them on by letting her out to play in the fenced backyard before you crate her again.
Stop pretending to be noble and at least admit its selfish. Its not like its new, cheating has been around for as long as monogamy.
I am married, monogamous but would be into poly stuff if my partner was. But she isn't and im not going to force that on her. Its called consent, you should try it.