The thing about a situation where one partner does a lot more of the earning, the other more of the home stuff, is that it has to be by mutual consent. Each partner needs to value and respect the other partner's contribution, and to say so, regularly. Both should be equally satisfied (even if its only 75% satisfied on both sides because of unfixable issues such as ill-health or whatever) - and the arrangement should be under regular review, to determine if both feel its the best - or at least the least-worst - split for the time being, and also review at least the possibilities for the next 5 years as kids move to different stages etc.
At least this is how dh and i manage it. I am the low earner and I regularly check with him he's still comfortable with that (not childcare these days, I work at something v poorly paid but that we both believe is important, and as he says 'we have enough money'.
This clearly isn't happening in your home and resentment has built up. You're both very pissed off with each other.
I think you need to try to explore in a very factual, spreadsheety sort of way, what the possible options for rebalancing would be. What would be the implications of you changing role and/or reducing your hours. Would you lose your home, or is it in the realm of car finance/holidays/sports club membership etc?
If you took on one 9-5 day of husband's chores, homework help etc, what could he potentially earn? Does he have a reason for not doing that? Would he commit to a more regular paid job if that was't happening
I worry that you might be placing your lifestyle before domestic peace (£600 sounds quite a bit for an item you've managed without for two years, so I am guessing you are well able to feed, clothe & house yourselves?)
I think you should explore a range of different options in a factual, spreadsheety sort of way, with both of you able to propose scenarios so long as they are also able to set out the financial and time-allocation implications realistically and honestly. If you make it clear you want to do things in this detail, perhaps that is the way he will 'get' that you can't go on like this.
You may even find that you don't actually want to relinquish the status, income & future prospects of your current role. Whatever the details though, you both need to be able to be honest and realistic with yourselves and each other about what is possible for each of you, and what you both need.
If this kind of conversation isn't possible I cant see how this is really a marriage :(