He would have to pay you £1697 a month in child support.
In any divorce, you could pursue him for Economic recompense, if your career has taken a back step to care for the kids.
He has to share his pension with you too - as alot of people don't want to wait until retirement, this is often facilitated by the person with the smaller pension getting more out of the financial pot (house equity).
You need a very good lawyer. You'll be amazed at what you're entitled to Op.
FWIW, my first H had a lot of dalliances. The ONLY time he actually listened to me and took stock, was when I announced we were over. Then he regretted everything and begged me to stay. Nothing else before that opened his ears.
I would do the following :
Consult a divorce solicitor and get them to draw up a separation agreement which shows all the assets and the proposed split (hugely in your favour as your pension will be less than his)
Print off the CSA calculation showing what he has to pay you
See what benefits you might be entitled to
Figure out if you can afford to keep the house, once you've taken into account all the finances as per above
Tell her husband what's been going on
Pack him a case & tell him to leave. Ask him which solicitor he will be appointing, so that your solicitor can send on the separation agreement to them
Tell his parents what's happened
The above will scare the absolute shit out of him. It will most likely nip the whole thing in the bud. But I wouldn't want him after this.
FWIW, I did follow through and leave my H, but it took me 4 years to do it! I just fell out of love with him. Over that 4 years, I started to notice other men when I went out. I'd always had blinkers on before. Then I actually had an affair myself. I realised that "other men are available".
I left him, and 8 weeks later met my wonderful DH. Been together 18 years now. You deserve better than this - hell everyone deserves better than this! You are no-one's back up plan, FFS.
How fucking dare he! Find your anger Op.
And defo calculate the financials, Knowledge is power.
My ExH was very disgruntled that I walked away with much more of the house equity than him, due to the fact that his pension was larger than mine.
Boo fucking Hoo.