You are BOTH working overtime.
He is getting paid for his, plus getting kudos for being the provider.
You are working 30 hours a week, plus doing all of the "unseen" and certainly unpraised labour of raising a child, doing the cooking, cleaning, laundry etc.
He should be doing half the childcare plus half the housework, and instead he's forcing you to do his share, whilst he does paid work.
This leaves you in a financially less secure position, especially as you're unmarried, as his igher income, is presumably paying more into his pension, savings etc, but he's only able to do this because YOU ARE DOING HIS SHARE OF LABOUR FOR FREE.
You need to have a sit down conversation with him about roles and responsibilities and say you are fed up of covering his workload because he is choosing to be elsewhere.
The only person he's benefiting is himself, and as you say, you'd be better off as a single person without him, but he'd be much worse off without you.