She is being friendly and nice because she suddenly has lost her better option. So now you are not so bad. But this won't last, she will start looking for OM #2 to jump ship soon. You need to let her know that you know she has behaved badly to you and she cannot just turn around and assume everything is fine because she says it is. Things are not fine in the way that you have been treated. She has abused the marriage by using it as a safe haven from which to look for a new husband.
Now you are unhappy with how things are. (Yes, you exist in this marriage.) You are not interested in just being her safe haven. You want a real wife who loves you and wants to be with you. You are not sure if she can be that person. Ask her if she still planning to move out? If not, why not? if yes, then when? You have a right to know what is happening in your life, not to just passively accept whatever she does.
FIL is not looking you in the eye because he knows what she is planning to do. He is embarrassed by that knowledge. If it is move out, then she should do it, not spend all your money on home improvements. You can choose your own home improvements without her input. Why should you be the last to know what is happening in your life?
