I didn't really want to say it either, particularly because it quickly can sound like blaming the victim. But perhaps the baggage from your biological family has produced character traits in you that her family has learned to exploit. Such as an inability to defend yourself, and unwillingness to make waves for fear of reprisal, ect....
Just sayin', as someone who has had the "Letting them have it" fantasies with regard to their own family, and who has acted on it....goddamn it's liberating. You cannot know the satisfaction, of the look on the faces of people who thought they had you figured out and who now have to treat you like a person.
Bottomline, you are the only thing between them and the street. It is only by the love of your wife and your innate decency as a person that you have done this, and they have quickly extinguished the latter. That is your power, man. Exercise it. And honestly, if your wife is part of the same deadbeat behavior you see in them.....maybe she needs a wake up call too. Because in a way she's exploiting you too, only from behind the shield of marriage.
You're seriously holding all the cards, you just need to decide what hand to play. And remember really it's just your wife who has any hand at all, and it sounds like a pair at best. And what ever you say you will do, mean it. I mean, think about it. On one hand, you'd have sooooo much more money to do with what you like because you're no longer supporting an entire family if you kick their asses to the curb. Or, on the other, you either scare their asses into getting a job, or at least doing something to make your life better when you finally assert that it's your house, your money and your goodwill that affords them anything. I mean....it's how my parents got through to me as a bit of a spoiled brat. Tell them you expect chores to be done in exchange for this magnificent rent-free gift you give them. Dishes done, house vacuumed, bathrooms clean, yard picked up and mowed. When they want money to rent movies ask them "What have you done for me lately to deserve this?" If they do none of these things, give them nothing. Treat them like they're 12 if they're going to act like it.