Welcome to MarrriageBuilders, C&D...
Have you read on this website the Basic Concepts, coping with infidelity, the four rules of marriage?
You know understand that relying on your WH to tell you the truth isn't reasonable...because he's in a fog, really, of his own truth...and to cheat it takes lying to ourselves and to others.
Don't lie to yourself. You've laid it out really well in your post...you know your WH doesn't protect his marital boundaries...you chose to believe he would protect his own weaknesses given how hard hit he was by previously unfaithful partners...that's what I heard you say.
Doesn't work like that. If you'll read "Surviving An Affair" by Dr. Harley, I think you'll find out more of what infidelity is, (emotional affairs EAs...physical affairs PAs) and here on MB, you can learn what fog is...a wayward mindset...for A's begin in our minds first...
I would also suggest you move your post (copy and paste) to Infidelity: General Questions II forum...it gets the most traffic...your marital issue is really about fidelity...and what isn't...and there are a lot of people over there with great advice for ya.
Reasonable to me to feel confused when your WH is saying one thing and doing another...and you know he's doing it. You can't make him say it...yet, you know this and keep asking him. So cut down on your own dazed/confused feeling here...because you keep taking the same action and expecting a different outcome.
Projection is what he's doing, IMO, with others who cheat...don't cheat yourself from other military wives who have been in your shoes...with wayward husbands...because it takes a lot of self-deception to act unfaithfully, he can easily see in others what he refuses to see in himself...and judge them harshly...stay away from them...and he can't do that with himself, can he?
That's my take...'cuz I lived it. You can recover your marriage...by learning, studying and focusing on your own choices...going for clarity, not fixing...
Thank you for being here for your marriage.
LA