Rob,
My personal opinion is that owing to the age of your daughter, you would effectively be tied to the mortgage on the FMH for another 12 years or until your wife cohabits. It is a hefty mortgage and I think that in order to for you both to provide long term accomodation for your daughter; the sale of the property is a good idea.
Your wife may be entitled to a larger % of the equity (both due to her earning capacity and depending on the difference in value of your pensions). I don't think it is unreasonable to expect your x2b to move into a 2 bed property. She may then be able to take on her own mortgage, owing to her salary and her share of equity as a deposit.
The fact that you have shared residency goes in your favour in relation to the above in my opinion.
As for Child Maintenance and Spousal Maintenance. Base CM on 15% of your take home pay (but make a 50% reduction owing to shared care). Not quite sure on SM when you have 50% residency. Your wife will be entitled to an amount of Child Tax Credit, don't think it will be much, but she would get assistance if paying for childcare.
I would find out how much, take home pay, Child Benefit and Child Tax Credit your x2b gets and then compare that with your take home pay. Maybe you could agree to give her slightly more equity as a
Clean Break as far as spousal maintenance is concerned.
You can fill in a
form E just for ease of collating information without the need to take it further. Another way to discuss finances is through
mediation, they provide forms to fill in, a bit like a form E and any agreement reached through mediation can then just be formalised through a solicitor.
If your x2b refuses to sell the house your only option would be to make an application for Ancillary Relief and then costs start to rise.
Hopefully, your x2b will see selling up makes financial sense.
Hope this has helped.
I will just say that if anyone thinks I am selling his x2b down the river, I am not, I just think it makes financial sense to all parties. Yes, I am fighting to keep my house, but I have 5 children to house and that isn't as easy as finding a house for you and one child. No I am not on the defensive, just making what I say as clear as possible.
Regards, Sarah