Ok...where to start??? First to tell you, you are not alone! My H has done all of the above...he left us the week before Christmas...I am his second marriage, I have two stepsons and two daughters from our marriage, they are 5 and 1.
Told me he didn't love me and did not want to be married anymore...OUT OF THR CLEAR BLUE....left...come to find out, OW is 28 and has two kids of her own. He is supposed to be living with his mother but only stays there when he has the kids...otherwise that living with OW.
My kids have not met her and will not until our D is final. H filed the end of March, we go to court in June. He still has not moved his things out of the house...only took the big screen tv and his golf clubs, and my stepsons beds. Thats it!
My H is like yours in that he is not attentive with the kids...He doesn't call them and only sees them because his mother says he has to. My MIL/FIL are very supportive of me and the girls but still side with him...basically he is using them and doesn't care.
I am sure your inlaws want what is best for the kids but be careful how much you say to them.
When H mentions divorce, ignore it. If he wants to file, he will.
As far as money, my H did the same thing. Kept direct deposit into our joint acct until his lawyer told him to stop and open his own checking acct. H has changed credit card numbers so I no longer have access to them (sneaky!) None of this is characteristic of him at all!
Now, the money has stopped coming in, he has lost two jobs and his life is a mess. I am hurt, disappointed and disgusted, not so much with how he is treating me but more about the kids...
My advice to you is to GAL, do things with the kids and things for you! Try not to let this consume you too much...I know it is difficult! Don't give him tons of information about the kids...let him ask the questions,,,only answer the bare minimum...Let him know what he is missing!!
Not sure what happens to these men....it is like a switch gets turned and they are someone we don't recognize.
Your H may just need a break (not saying it is right!!) As far as OW, act like she doesn't exist!! No matter how many people think he is wrong until he realizes it nothing is going to change...remember an OW is a bandaid...a "feel good" for the moment...it will not last! Keep your kids safe and protected through all this...
Your H is acting like a typical MLCer...the more you read here the more you will understand it! Vent here...we will listen...do not beg, plead and ask questions your H doesn't even know the answer to. Do that here and we can help!
It is a long road...some here have been lucky enough to come through it with their marriage intact. Like I said, do things for you and put you and your children first. Detach from him and let him see what he is missing. If you are trying to talk to him about the relationship he will not have a chance to reflect.