Infidelity Support Group
Any relationship in which one partner engages willfully in sexual relations with another outside of the partnership is considered to have experienced infidelity. This breach of trust is often traumatizing for the faithful partner as well as the relationship, and support is often needed to heal emotionally and to decide whether or not the relationship should continue after...
This has been the best article I have found on what needs to be dons for the BS to heal.
If you agree send the link to him. And good luck dear.
I'm so sorry you are going through this. Nothing will quell your need for answers until you have the answers, as you may have discovered.
He is not in any position to be able to help you in this way. And unless you have some hard evidence, he'll gas-light you and keep you in the dark.
Have you sought some individual counselling to help you alleviate some of the pressure you're experiencing? A therapist may be able to help you take a direction that you haven't thought of.
I must say that age plays a role here in that he is probably not emotionally mature enough to handle what he's done and he knows that you will not be so accepting once you find out the truths.
It may take some investigative techniques on your behalf to find the information you're seeking, but I wouldn't except him to step forward anytime soon. The more you try to get things out of him, the further he'll dig his heels in.
If you feel that you are "in a deep hole and can't get out", it may be because you're relying on him to help you, and that's not happening.
I wish you well.