So combined household expenditure is £3,300. Of combined household income, his share is 75% whilst your share is 25% (as he earns three times what you do). He is paying for 70% of household expenditure while you’re paying for 30%.
You are paying (slightly) more than your fair share of combined household expenses based on income.
However what concerns me is that he is paying for the capital elements of your household and - and making sure there is a record of that - and making you pay for the consumables.
If he decides to end the marriage, the non-consumables (the house and its fixtures and fittings) will still be in physical existence, whereas the consumables which you’ve paid for - the childcare costs and the food - will no longer be in existence.
I’d be concerned that if the marriage comes to an end, he will try to claim a bigger share of the property and the fixtures and fittings, by arguing that he paid for them. He’d be able to use the significant savings he’s built up - thanks to you deprioritising your career, your income and your long term financial security, and thus permitting him to prioritise his career, income, and long term financial security - to pay for lawyers to screw you over financially get him the best deal
His use of the phrase “cash cow” whilst benefitting from your free labour in the form of childcare and housework worries me. That suggests that he sees your marriage as a short term arrangement not a lifetime commitment, and that he sees you as Domestic Help In Human Form that he’s paying for, not as his equal partner.
Also any man who expects the woman who’s risked her life to provide him with offspring to fund her maternity leave from her savings is, at the very least, lacking in chivalry.
You need to protect yourself by increasing your hours back up to full time.
Also make sure that he’s dong his share of the childcare and domestic labour so that you’re not running yourself ragged to enable him to have Very Important Career untroubled by any domestic duties.