It sounds like your solicitor is going to do a good job for you, lw.
Jusr remember what freckle said - that a mesher order actually offers the higher-earning partner a better deal in the long run - instead of the house going to the primary carer of the children for good, he gets his bit back once the kids are independent. He isn't losing any of his share of the investment at all - it just means that his sons (and the person looking after them for him) gets to live in SOME of his share of the house as well as their own share of the hosue.
Also remember, lw, when dealing with members of your family (who seem to have very old-fashioned ideas about partnership in a modern marriage - inclusing your bil) that all your childcare, parenting and housekeeping are of equal value in the household. The fact that he brought in more of the cash is immaterial.
A question I asked on your old thread, I think - does anyone here know anyhting about the mediation process? I think Freckle said it wasn't binding - if you find it too hard to fight your corner face-to-face with him you can just come out afterwards and tell your solicitor you still want the mesher order. I wonder if you will get a chance to speak in private with the mediator? it seems a bit of a joke that you have to spend time in a room negotiating with a man who you are leaving because of his anger, bullying and because he has at times terrified you! But hey ho. I am assuming the mediation means over assets in the divorce, NOT about your relationship??
Anyway, lw, if you keep enough of the equity in the house (under the mesher order) to be in secure accommodation, I suspect that H will be able to raise another mortgagem anyway, won't he? he'd have more than enough for the deposit if he sold the car!!! He can get a batchelor flat / apartment!!
I think the point your solicitor made about rented acommodation not being secure is a very very good one. The LAST thing you will need is to keep moving house if tennancies come to an end etc etc! Not with the kids and needimng to be very near their school etc. Keep that in mind when you stick up for your mesher order.
Anyway it is absolutely not one invisible jot of your family's business!
Well done for getting the appointment - you can do this!