I am so sorry this has happened to you
What a horrible turn this special trip away took for you.
Firstly the (relatively) positive: he did tell you as soon as you asked. I put this here because you aren't asking whether you should LTB, and he could have lied about it for months.
From my point of view, though, this whole thing is a very bad sign. Based on what you wrote, I'm trying to work out whether he is actually remorseful, and I don't think it's at all clear that he is. At first he was trying to cuddle up and saying he loves you (Guilt? Or, (quite possibly more likely) feeling horny and wanting to finish off what he started at the strip club). Then, he told you about it "casually" (trying to downplay the fallout, or legitimately didn't think it was a big deal? He should have been apologising profusely at that stage, if not the night before). Now he has "apologised profusely and promised never to go again", but is this because he actually acknowledges it was a revolting thing to do, or because he is in damage-control mode and scrambling to keep you while actually thinking that there is nothing wrong with what he did?
I personally would also be looking for him to be remorseful not just because he is sorry he upset you, but because getting a private dance from a woman at a strip club is a revolting, misogynistic thing to do regardless of whether he's single or not (in my opinion; if you don't think this, it won't apply) and he feels ashamed he did it.
Anyway, you are completely justified in being upset with him. It's natural to want to look to blame your DH's friend, who certainly sounds like a piece of shit himself, but it's important to recognise your husband made these choices himself. Do you want to be with someone who lets himself be led like this? Who will spend sixty quid when you are trying to save? Are you sure he isn't just putting it all onto his friend when actually he was a driving force in this? Does it even make a difference whether or not he was?
You didn't ask if you should LTB so I won't say more on that front but as to your AIBU to generally be awful with him for a prolonged period of time and to want to rip his friend to shreds you should want to rip your DH to shreds too. And also, if you are wanting to work things out with him, while you're totally justified in wanting to be generally awful to him and must NOT feel any pressure to "forgive" and let things go back to normal before you feel completely ready to do so, I think you also need to really talk about these issues with him, make sure he understands what your problems with his behaviour are, and make sure you get an understanding of where his moral compass lies.