Deep breaths OP.
Get some respite with mum.
Will work understand if you miss some hours today - are you able to flex them? Or explain that you could not WFH as your H was unavailable for childcare?
On the practical side - do you rent or own your home?
If you rent - are you both named on the tenancy?
How are finances arranged, & do you earn enough to support you & DC solo?
What does your H earn, & what would the CMS-recommended % of that amount to each month when you make him pay maintenance?
No need to respond to those Q's here OP! - but it is all info you are going to have to think about with a cool & hard head on. At your own pace, when you feel able to tackle it.
He's not going to want to look after his own kids if you split, so use the CMS calculator to work out what it would cost him should you obtain sole resident parent status. Add in whatever benefits you may accrue as a single parent by checking on the EntitledTo website.
Once you've had time to do that, gather all the important documents - your & DC passports, birth certs, etc - details of all sole & joint bank accounts, any savings, or assets like cars, pensions, equity if you have a mortgage ... & see a solicitor.
Don't tell him ANY of this.
Keep your cards close to your chest so that - for a change - YOU are the one in control of things.
Take your own time, see as much of your mum & good, trustworthy friends as you can manage, & keep posting for support. Your H is a gaslighting, controlling prick who is using you to run his household while contributing nothing to it & making you feel horrible into the bargain.
He does it deliberately, because living the selfish existence of a single 'lad' is more important to him than your or his kids' happiness. You owe him nothing.