He hasn't even tried has he? This is along reply so bear with me.
He's not stressed because he doesn't need to be when you're around! He thinks this problem will be solved, but not by him. You just need to ask your mum again and again until she folds. He's putting all the pressure on you to resolve the money problem. Unfortunately for him, your mum wants the best for you and sees this so has basically said 'no, if he wants my money he can acknowledge me by speaking to me first and only then he has to agree to pay it back or I will never see the money again'.
It's not difficult for anyone to establish that if your mum thinks this, she has seen more than enough to question his reliability and respect for her daughter (and her daughter's family). So when the deadline passes and he hasn't got the money from your mum because he refused to talk to her about it( read that again, just refused to talk to her) then you become the bad guy. It's your fault.
So then what? Well you will be the villain at home. I couldn't live like that, home should be your home, not a place you eat and sleep in.
You have choices still and so does he, but his choices will become extremely limited when the deadline passes. You can choose to support him and try to get the money another way or deal with what happens when it isn't paid, as a couple. Wider family relationships will continue to be strained but your family love you and will want to see you still despite your husband ignoring them. You'll have to continue to make excuses for his rude behaviour to everyone else outside the marriage but you will see your mum.
The stress you feel now at home and work will get worse because the serious consequences of not paying on time will continue to weigh heavily on you while he plays games ( in other words while he says he is not stresses for example) and the uncertainly of the future will grow. Your work will suffer and as the stress builds that will undoubtedly affect your physical and mental health, your work, your relationships, your children and your life. His attitude and treatment towards you will add more stress. This will confuse and isolate you and therefore you will have nobody to really talk to outside of family-or is that where you find yourself already?
Ask yourself where YOU are, not anybody else. You're in the middle of a mess you didn't create. What do you need? A hell of a lot more support, understanding teamwork, stability, reliability, respect, emotional maturity and all the other things you need but don't have from your husband would be a start wouldn't it?
Passports are mentioned because as long as he is on the birth certificate he has rights and sadly, some people have found themselves in a living nightmare when partners or ex partners have taken their children back to their country for a supposed holiday and just never returned. It happens. That's why people are saying hide passports if the children have one. Nobody is saying he will do this, but he could if he wanted to just leave.
Ok back to you -what do you think you need? Make a list of practical needs and whatever is lacking emotionally for you. What of all those practical things do you get from him? Can you get it from yourself? How? If not, how can you adapt?
From now on consider telling him facts, not asking him things. Asking him questions can stop-they are a waste of your precious energy.
He has to deal with this.