Firstly, I endured 14 years of basic contact with the mother of my children till our youngest turned 18yo then I told my ex never ever speak to me again. That was 11 years ago and she hasn't.
So, I have experience in such a situation. What is the best approach?
We'll I think your solicitor is wrong! You do not have to remain in that house. You can move some distance away, as long as such a move doesn't disadvantage your ex too much- seek a second legal opinion, it's worth it.
In terms of communication, until your child is about 10yo accompanying them to the car for pick up is appropriate. Ideal is "hi" and any reminders e.g. medication, education, clothing, drop off times etc but purely just a friendly manner. These things can also be done by text prior to the day. For the next 3 years just tolerate that and ignore any inappropriate comments, walk away. Bare in mind there will come a time when you'll need him, maybe you got held up and can't meet him and your child etc. Always best to be cordial but I learned, it takes 2 to make that happen.
I don't doubt your assessment of him but it's your perspective. Your child is in the middle and will suffer if you don't shake off these feelings. Ok he is condescending and says things that you don't like....but he is your child's dad and he obviously doesn't know what he's doing.
In an ideal world, you'd have a meeting in a cafe or park and write down a journey of do's and donts, boundaries and giving mutual respect. Your situation will go on for a while but 10yo maybe 11 your child can walk to and from his car and no contact required. Any official messages by text and that's good to have on record if abuse occurs.