Hmmm...you neglected to mention that she was all for this. Perhaps then they must be somewhat aware of her wild tendencies and therefore should not even think to put the blame squarely on your shoulders.
Your situation is very delicate indeed a sort of damned if you do, damned if you don't.
Let me ask you, do you have a contigency plan?
Could your webcam biz take a turn for the 'racier' than anticipated side? What if this potential storm with the in-laws subsides and then the cash really starts flowing in? Are you BOTH involved in the decision making processes here?
I don't want to make you feel nervous or insecure in anyway but YOU must somehow have YOUR ASS covered. I'm not trying to put down your wife at all - hear me out here. You did say you feel you are kind of along for the 'ride' so to speak. That you had a secure source of income for the next 20 years?
Seems like you've compromised yourself for the oldest trick in the book.

Not to worry. You are going to have to develop a contingency plan for you, Juggs. Obviously something is not proper within you. If you are comfortable in this situation then I apologize for jumping the gun here. If not, think where this might be headed. There are usually Three possible outcomes: The Good. The Bad. Or The Ugly. *cue the spaghetti western music*