Being Poly isn't a default setting you can (our should) switch to when your relationship isn't working out. It takes a very strong and stable relationship to survive, let alone flourish. If your mairriage is already in crisis, opening it up to other potential lovers will only make it worse.
What you need to understand is that it is possible to cheat while being poly. Any relationship that doesn't respect your partnership with another (or others) is cheating. The infidelity you and your husband repeatedly inflict on each other is negating any chance of having a healthy traditional relationship, let alone a poly one.
Try following this course of action:
- Step 1. Put your other relationship on pause and fix your situation at home, to include stoping all communication wth the other man. Emotional infidelity is just as dangerous as the physical version, and it undermines the intimacy you need to invest in your marriage.
- Step 2. Honestly (and I mean HONESTLY) discuss what both of you will need to open your marriage safely.
- Step 3. Maintain honesty, and respect each others feelings as you migrate into your poly relationships.
- Step 4. Repeat Steps 2 & 3 when things go wrong (and don't worry, they will.)
This has been my humble and unqualified opinion. It's worth what you paid for it. I wish you and yours the very best of luck.