@millymollymoomoo’s advice is good advice.
Fundamentally, the welfare of the child is the court’s first priority.
Also, the court will look at potential as well as current costs and earnings. If there isn’t enough money to house everyone and NRP can work but is choosing not to, whereas RP cannot work and maintain the child’s needs, it is likely that the court would expect NRP to up their earnings to meet the deficit.
Where there isn’t enough to go around, a clean break is more difficult. So you might be stuck in a financial arrangement with this guy for some time.
Given that your ex sounds pretty intransigent, I would see a lawyer as an investment in your future here, to get the best result for you and your kids. Some family barristers and family solicitors do ‘packages’ so that there are minimal unexpected costs - maybe worth contacting a few and asking.
Do not give up on his pension just because he doesn’t want to talk about it. If a share of the pension is what is best for the kids and equitable for you, it’s only reasonable that you pursue it - and personally, I’d want a lawyer to do this as pensions can be complicated.
Good luck OP, and sorry your ex sounds very difficult.