Fair enough Sara, vent away. i don't know how you have stood it for this long. My dad sometimes tries to parent my kids and I have to step in and point out that I am their mother (and I am not exactly a child! even though he sometimes treats me like one) I don't think its dong your health or your marriage any good having them in the house, Brent needs to realise this but being a man he won't LOL
Your MIL should be sensitive enough to realise that 2 women in a small house is not going to work and since there is an alternative she should be moving out to the flat.
Hope your day improves hon.