Whenever you feel the need to engage, do the opposite, confrontations need more than one participant. Detach, detach, detach
100% this!
You can't win an argument with these manipulative types. I've seen my brother go through something very similar to you and your ex wife. She seemed like the perfect wife material for 20 years, to the outside world she was whiter than white and my brother enabled this and also defended her, kept her abuse (emotional) quiet. He also said there were times she became physical.
I don't really know where to start with your post, it's like my brother could have posted it.
DW exploded and managed her usual beat-down that somehow ended up with me apologising for it all
My brother said exactly the same. His ex wife was going out to meet the OM, this was only a few days after my brother discovered her affair, he confronted her about how she could be so insensitive, couldn't she see he was it bits. In the end he ended up apologising to her.
When things aren't going her way, out comes a horrible
Typical manipulative/narc behaviour, she knows you hate confrontation and uses this against you. Don't be frightened to stand up to her, that doesn't mean arguing with her, ignore her, detach. she'll no doubt rage over the fact you have disengaged from her. Keep at it though. It's called "Grey Rock" technique, google it, it works.
Solicitor
you've got a solicitor, great. I hope they are good solicitor that can fight your corner, your ex has no respect for you or what you want. Spend the money on a solicitor if you have to, it may cost a lot but could save you thousands more in the long run. My brothers ex told him that they should try and settle without solicitors, he tried this doesn't work with manipulative people. His ex raged when she things weren't going her way, again prepare yourself for more anger and rage from your ex if things go down this route.
mildly gas-lighting me and taking advantage of the fact I am on Sertraline for depression and anxiety
Theres no such thing as mild gas-lighting, again classic narc behaviour. Trust your gut.
I definitely feel now that although she wears the same face, this person is definitely not my wife, and I am finding it increasingly hard to be 'friends' whilst this goes on
She wears a mask, The person you thought she was is a lie. Don't be her friend!!! It's all about Her image. She wants to maintain a facade to the outside world that things are OK between you.."See we are still friends, despite me being a cheating bitch".
Do people know what she's done or have you kept it between you for the time being?
wtf do I do when the fucking monster comes out
Detach, ignore, grey rock
When I was bullied in school
Your ex is a bully, she's no different to those people at school
Go to this website..www.chumplady.com
read all you can about narcissism, covert narcissism, manipulative people. Read all you can, watch you tube videos dadsurvivingdivorce on youtube might help you.
You will get through this, you need to be strong, you need to be prepared to go outside your comfort zone. Your kids will win if you get out of this marriage, get back to who you are, trust me you can do it. My brother is in such a better place, he looks great, he's off any medication, he's healthy, he's the brother i used to know.
NEVER GIVE UP