I may have missed this, but has your husband actually been leaving his stuff out in the open?  Or is it "not-very-well-hidden?"  

I agree with others who have pointed out, he's trying to pressure you about your daughter because he's isolating you.  I now see what I hadn't seen when I was in your position: that it's absolutely exhausting to keep the lie going, day in and day out, for years.  My husband got to a point where he seemed to dislike having anybody in the house other than me.  He was pretty vicious to my daughter, and I now see that she was making his situation twice as much work.  He actually said, once when she came home from college over Christmas (and this is a direct quote): "Why do you even come home?  Every time you come home, you ruin everything.  Everything is perfect until you get here."  

But one thing I think you should be aware of: if you sit your husband down for a talk, it's going to make a huge strain in the house with your daughter living there, but not knowing what's going on.  I think you should plan the conversation around a time when she'll be away, at least for a weekend or something.