I always hesitate to shove my head into the fray in discussions like these... but here goes.
The discussion of the sex industry is a separate one to your relationship. To me, I would not describe your husband as a liar. He was committed the sin of omission, if you like, but has not actively lied. Yes, you can say, if you want, that a lack of truth is a lie, but we all fail sometimes. He probably just never knew how to bring it up - because he knew it would be a massive issue and didn't want to demean himself before you. Clearly, he should have thought about that before he went off with his boss - and that could be a weakness - but many people are drawn into behaviours by a group mentality, or by a perceived stronger person that they wouldn't countenance by themselves, in the cold light of day. And everyone can say 'he should grow some' - but maybe we can all think of a time when we have done something unworthy because of the situation we found ourselves in.
Secondly, you said something at some point about your previous relationship. This is not your previous relationship - and if you behave with the defensive patterns you have acquired from being hurt previously, you are more likely to bring it to an end. As far as you are able, I would say that you need to judge this relationship on its own.
Thirdly, it's a marriage. I find it difficult to understand how so many people I see on these boards are willing to end a marital commitment at the first evidence of failure. Clearly there are situations when a marriage needs to end, but that it is a personal and societal tragedy, I think - and shouldn't happen just because one party is a bit weak or doesn't quite fulfil the expectations of the other.
Fourthly, yes - I have been to strip clubs where it was evident sexual services were also being provided. I've seen men taking their clothes off for money, female strippers brought into the workplace (where some poor sod having a birthday was clearly uncomfortable and doing his level best NOT to touch her while she shimmied her arse in his face) and known someone who worked in a lap dancing club. I find the whole thing rather bleak and depressing - apart from the one instance of a carer paying for sex for his relative with Downs Syndrome. Which is the start of a whole 'nother conversation... However, we have no idea what went on in this private room and everyone being so certain that they do is just implanting images in the OP's head which have no right being there.
I can see that this is a shock - and disappointing - but for me, it wouldn't be any more than that. I certainly wouldn't rank it with adultery. And I would also be looking at myself to wonder why my husband didn't feel that he could tell me. Before everyone jumps on me, I'm not saying it's the OP's fault - but if two people are working to the common goal of a long and happy marriage, there's nothing wrong with both parties assessing what they could do differently to achieve that.
I would also be supressing the desire to punch the messenger into next Tuesday... 
She clearly has issues and is no friend of yours.