Thank you for your question
My name is Clare
I shall do my best to help you but I need some further information first
Why was the 95/5 split agreed to start with?
I understand then why this was how it was put in the Transfer - but what was the underlying agreement between you about how you owned the property (if there was one!) this is important in working out what a court might decide (which is what you need to know!)
There are a number of ways of addressing this - but to deal with the specific questions in order
1. Percentage shares
2. You are making the calculation too complicated - it is impossible to do much more than take a broad brush approach for instance the deposit was shared 70?30 with you making the latter contribution at the start - but he made the larger contribution thereafter so they balance each other out
3. If the house was being sold then you would both "loose" money on the sale costs - so simply agreeing that you will use the proper value and not make a deduction for notional sale costs would be fair
So a starting point of 50/50 might be fair BUT you could equally argue that in fact whilst he paid more of the mortgage you were caring for the children - which will impact on your long tern employment and pension position - so sticking to the 70/30 split that you paid the deposit in would be fair.
I hope that this is of assistance - please ask if you need further details