He needs to look into what redundancy pay he will get and apply for whatever benefits as soon as he can.
You need to ensure you are getting all the benefits you are entitled to, look to improve your work/income situation, make sure the CM is right, claim child benefit (surely that must be on top of your £800pm?) and support him through this period however you can.
I think if he was happy with your contribution then it's fine, it's proportionate to your incomes. But the situation has changed and unless you all want to be homeless, of course you now have to help out more.
If you don't want to help then you need to re-evaluate the whole relationship.
If he is really bad with money and this cannot be fixed, then you need to re-evaluate the relationship, I understand, I am a saver and low spender and I can't live with people who are bad with money, it just doesn't work for me.
I don't actually think you should pay half each. I think he should pay the mortgage and you should pay half each of the remaining bills, plus you pay a token towards 'rent' - which is more or less what you have been doing.