Welcome -- and keep talking to wife about your boundaries. For you -- note how you talk to yourself about yourself in your head. Comparing, talking down, etc. Work to become secure in yourself.
Read things together --
is a good starting point. Esp the pitfalls one
and opening a monoship
. Plan how to cope with jealously.
Labriola also does pitfalls here.
There's more at
Do you guys communicate well
and have good interpersonal skills?
How do you do conflict resolution?
Perhaps the counselor can help you work on those. You may consider changing to a poly friendly counselor
-- because if the counselor urging her to break it off with the other guy becomes an obstacle to good communication with wife and you both regaining marriage health then that's not good for the marriage.
Read things together and if/when pitfall moments hit, have the plan for how to navigate through them.
But before you even go there... if you do NOT want to be in polyship at all? This is what you arrive at after your soul searching? Don't. It's better to split up that to do something against your willingness.
I cannot tell if you are willing but nervous, or unwilling and feeling like "Ahhhh! What did I get myself into? It's too late!" like you are on a runaway train. How are you feeling?