I think you need to get out now via the womens aid route.
I was giving you some thought over the weekend.
Firstly, thinking that fil will co-operate in you splitting up with his son and evicting you. My ex's own brother told me he didn't know why I was still with 'that loser' (his own brother) and told me to leave. When I did, his family closed ranks against me and made things very difficult re the house and his brother drove him round till he found the car which I had taken (thought an old car was a fair swap for a house with equity in it), he realised I must be staying with a friend so he got his brother to drive him round all my friends. Next think I knew there was a copper at the door saying he'd had a report of a stolen car and trying to arrest my friend's husband because it was on their drive!
Word got round quick and no-one would help me with accom etc, and I had no dependents so right at the bottom of any waiting lists.
do you think that your H will agree to a divorce, let you stay in the house until your fil has issued you (or both of you) with eviction notice, then stand by while you pack your bags and take the children Do you really think that after all this you will just leave the marital home and go to some new place all set up by the council?
Your husband likes to control you and make you feel incapable of doing anything for yourself. There is no way he will let you get away from his control.
I'm going to be harsh now but I'm only speaking as one who has been in your situation. I honestly think you will HAVE to have some upheaval and it might be horrible at times. If you go through womens aid and have a brief stop at a refuge or safe house, you will get somewhere from the council sooner and you will be among women who've been having similar experiences.
I told my ex that I wanted to go, at that time I wasn't sure how exactly I would go about it or where I would go. At first he was nice and said he'd change, so I thought OK I have some time to save up. Then he started again but it was worse than before. As if he knew that I would leave if his behaviour got bad again, so he really concentrated on making me feel like I'd bottle it so I'd have to put up or shut up.
In the end because I dithered, I ended up literally running out one sunday afternoon with just the clothes I stood in and my car keys.
Don't dither. make all the plans you have to, take documents and clothes to your sisters, and don't hang about waiting for that solicitors appointment because a) you have no house to have any claim to and b) she will think you want to arrange a divorce while I think you need to get out first and then divorce him when your self esteem is better.
Sorry to be harsh. But you've got a difficult time coming up whichever way you do it and I think you should go for the short sharp shock approach and then you can get on with your new life all the sooner.