The first question here is the
FMH and what happens to it.
There are a number of options here :
1. The house is transferred outright to your wife ( highly unlikely )
2. She buys you out ;
3. She is given the right to live there until the children are no longer dependent, at which time the house is sold and the proceeds divided ;
4. The house is sold now and the proceeds divided.
There are others but they are much less frequently encountered.
I simply do not have enough information to work out what is likely in your case. Remember that the Courts' priority will be to make sure the children have a home. But maybe, if the house is sold and your x2b has a new partner, a sale ( thus getting rid of the mortgage ) and both of them buying another house, and you getting a deposit to buy one on your own account, is at least a possible solution.
One thing you have to remember is that if you are a party to the mortgage on the FMH you remain liable unless released and this can compromise your ability to get a new mortgage.
About your x2b's paramour - no, he hasn't any claim in my opinion.
Whether the Court will take your new salary into account - yes, in my opinion, provided it was not just a temporary measure. Orders for SM can always be varied on the grounds of changed circumstances. Set against that, the fact that your x2b has a partner will affect SM because the Court will assume he will make a contribution towards household expenses, which reduces her needs andf therefore her need for SM.
I advise you to read an article ' Maintenance, re-marriage and Barder events ' by Marilyn Stowe which you should be able to google.
I also suggest that you take legal advice before you get too deeply into this. There is far more to this query than meets the eye. You don't mention pensions, and these can be important.
Mike 100468