New here, new to potential seperation

Hi all, stumbled across here as in what seems like the end of a relationship with 2 very young children unfortunately. 

Apologies if this kind of information is on here already and I will more than likely seek a solicitor soon; also if I’m waffling please stay with me as I’m not in the best place mentally right not, but just after some advice for my situation if possible financially if we do split.

I’ve been with my wife for 9 years, she owned a flat before we met (she bought 18 months before meeting me). From day one i paid half towards mortgage, bills, food etc and we got married about 2 years later. Before we got married I offered to get something drafted up on the property so if we split I couldn’t take half, I thought this was being nice but in the end she decided not to do it.

Fast forwards to last year, we’ve had 2 kids so decided to move to a bigger house with a much larger mortgage. My wife was made redundant so I’m making all the payments whilst she looks after the kids, fine. But in the week before we are due to exchange (it was a long process; big chain etc) she after all these years gets a trust in deed done by a solicitor. The equity was about £180k but she’s worked out my payments over the years and said on the deed I would only be entitled to £20k (she worked out my mortgage payments over the 7 years to reach this figure) if we split. I challenged this, I still had no issue with signing something, but felt the portion should be higher because I’d paid half for 7 years and I was now paying the whole mortgage/bills etc with no idea when she’d go back to work. All I really wanted was 20% (about another £15k), but she’s stubborn, refused to change it and said if I didn’t sign she wouldn’t exchange on the new house. This caused me untold stress and for the sake of my boys (I didn’t want them in a flat anymore) I signed.

Unfortuately since we moved in ive found it difficult to move on from her doing that to me, there’s other things but that was the straw that broke the camels back I suppose. We’ve been to therapy etc and even the therapist said she doesn’t think we can come back from this.

Regardless, if we do split how important is that trust in deed over us being married? I really don’t want to take loads of money, I just need about £30-35k to get myself my own flat if we split. 

I have a pension probably worth about £25k more than her (mines £70k, hers £45k), I have some shares at work although many haven’t vested (does that make a difference?) of about £25k. And she has about £40k in her bank (we kept back £15k from the original £180k equity which is in this figure plus her redundancy.

She’s still out of work and obviously we have the 2 young kids. Am I totally screwed if we try mediation here? Appreciate no one on here can give absolute answers, but some guidance as to what might happen financially would be appreciated.