RainbowsandUnicorn: What's so awesome about studying whilst out of work?
Once again, I didn't say she was awesome for that alone. Read what I wrote in the above post to April.
If OP was a single parent,
Based on her description, it seems that for large parts of the week, she more or less is in practice, even if not on paper. And if you want to go back to the "but he earns money so she's not single" line, if she divorces him and becomes a true single parent, he would still have to pay child support and she would reduce her workload since she'd no longer have him to tidy up after. She might also get the chance to leave them with him and get some evenings, weekends, and holidays entirely to herself. He'd actually probably end up doing more if they split.
working full time and studying it would be awesome
She is working full-time - taking care of her preschooler, doing the household duties, and picking up after her DH. Money may not come in from that, but just as importantly, money is stopped from pouring out because of what she does.
but when you have all day free every day
You seem to keep forgetting about this preschooler - you know, the one that isn't in school yet? And the fact that OP does the majority of the daily household duties, including picking and carrying after her DH who thinks he's too important to tidy up after himself. That is not "having all day free every day".
with someone else paying for it then it's hardly hard work.
After everything that's been said about how she is saving their household a ton of money at a direct loss to her own career advancement and salary progression, you still come back to the "someone else is paying" tripe? OP has probably done more hours in the early slog of baby/toddler parenting than her DH will do at his workplace in two decades. Her training ultimately benefits all of them in household security, a better income, and setting a good example for her DCs. This notion that her training is somehow a "perk" or a "bonus", and that it's not hard work with a preschooler around plus two other DCs to take care of outside of school-time and all the other household duties to take care of is just mind-blowing. Yes, other people have it harder. That doesn't mean OP has it easy.
These kinds of arguments are exactly why women's time and achievements and careers are substantially devalued in society.