People generally behave the way they do because those around them (ie. us) let
It is true that an ultimatum is often an excellent shock-tactic wake-up call for a person, and all of these MIL's sound like they are coasting because they can?
Maybe the ones who have lost their jobs feel depressed and unmotivated?
Perhaps in each of your families, you could all (determindly, and ignoring any objections) get together and work out a 'moving-on' plan, which involves finding alternative accommodation, a support network, possibly some form of education/employment. And persevere with it(!)
Realistically - it is your home and you have the right to feel comfortable and secure in it. Either give them VERY clear boundaries about what you will and will not expect from them behaviour-wise, or remind them that they have the personal choice to leave. But you must present a united front with your other-half, or obviously it won't work. Work out what you and your beloved both want from the situation, making sure you are both on the same page.
Oh, and you could always be wonderfully manipulative - appeal to them for 'help' with things, then slowly give them a whole load of chores (cleaning, childminding, shopping, relandscaping the garden, picking up the dog-poo etc) so that they either behave, or get fed-up at being 'used' and leave.
It's a complicated situation I know, but you
also have freedom of choice and the right to live in a decent environment. As adults you are all much stronger and much more capable than you give yourselves credit for.