Kiwimum - I feel qualified to comment on your OP, as I am married to a farmer and we run the farm between us. We were also an all year round calving dairy herd before we sold the milking cows in Dec to concentrate on arable/sheep.
DH is traditional in his outlook, in that he was brought up to believe that he provides for his family and his wife should be SAH and supported/provided for & the majority of housework/cooking/etc is done by his wife. He gets up at 6am and probably works through until 8pm most days on the farm. I tend to do all the office based work, so I am more SAH.
(This info is just to give context, BTW).
BUT and this is a HUGE BUT - if I am out, or away, or doing something else, he is more than happy to help. For example, he'll put the washing machine on if I ask, unload the dishwasher, put the hoover around and generally help with domestic tasks, because we're in a partnership. he's also capeable of getting his own lunch, cooking dinner on his own (not that he does very often, but he does). He also has certain tasks which he considers his, little things, like shutting the chickens in at night, feeding the dogs and switching the electric blanket on before bed.
If my DH only worked 5 hours a day an the off-season, he'd be doing a damn sight more around the house. He really would. And if my DH had the audacity to say what yours did when your DS was ill, he would have got the very sharp end of my tounge!!
It comes down to consideration and respect for each other. It seems to me, reading between the lines, that your DH does not respect your role within the household. He somehow sees it as "inferior".
I would be having a very stiff talk and laying it on the line, TBH.