So your husband used to make a lot more money, because he was working in his families business, which he was kicked out of.
Does he actually have any formal qualifications that would make him eligible to get a better paid job, or is he basically an "unskilled" worker?
With his history of being fired, he's also not going to get good references from former employers, he's a major risk for new employers so unlikely to get taken on, over another candidate. Would his families business not take him back?
You say he's working all hours in his current job, and as a delivery driver? Driving all day takes a lot of concentration (my dad was a delivery driver for many years) and can be very tiring, he's probably exhausted. With all the will in the world, your husband can't magic more hours in the day to be able to work, or insist on a higher salary or pick and choose a better paying job just because he wants/needs more money.
You're only just getting by, you don't say how long your mortgage term is fixed for if it is a fix, and if its not, or it runs out soon, current rates are astronomical, you definitely won't be able to afford any increase (and thats before the cost of food, fuel, energy etc also rising added on top).
You've reached your saturation point, your income cannot absorb any more costs, and yet they're almost certainly coming. You no longer have the luxury of living life how you want, but instead how you need, in order to provide for your three children. Because surely as all must agree, your childrens needs should be everyone involveds priority here. You have never previously had to work, and you don't want to work, but in order to keep a secure home for your children and food in their stomach, you need to atleast try. Both you and your husband need to adapt and let go of your ideal cultural roles if this is going to work out. He needs to become involved in house running and upkeep and some childcare, and you need to earn some money to help provide financially. Ultimately, if BOTH of you aren't willing to bend and work as a team, then you'll probably end up unable to pay the mortgage, and have your house taken from you, with no money in return to show for the years of mortgage you paid, and 3 kids homeless.
You see him as being financially abusive for expecting you to work and earn, but you are being equally if not more financially abusive expecting him to provide the funds to provide for FIVE people by himself.
By all means, continue to be selfish and insist on doing what you WANT and put all the blame on him, instead of doing what you NEED to do for the welfare of your children. But know it is JUST as much on you as your husband if/when your children inevitably suffer.