aaaaaaaah crunchy mommy you are my long lost sister.
first please know that you have an illness which makes it doubly hard on you. just being around a HNs child is extremely tiring.
you also have my dd's twin - just the opposite. she was over the top sensation seeking (needed messy hands and still does). also i think if you havent thought about it, from the little things you have said - i am guessing your son is 'gifted' too. (please i dont want to go into debate over this). and THAT by itself is further exhausting too.
dont be confused by all the checklist and to see what your son falls under. i know for my dd she had mild case which pretty much disappeared or toned down by the time she was 5. use that more as a guideline to figure out activities for your son.
the good news is your son enjoys sitting and playing. make your house a sensory place. at your son's age i gave my dd a pasta 'bowl' (i forget what the exact term is). i emptied out a couple of bags of those squiggly colourful pasta and threw in little articles from the house in there, like my tea strainer ball, little toys, spoon, small measuring cups, measuring spoons, textury things. yeah initially she would chew on the pasta but i kept asking her not to eat it and in time she got it. but she could literally spend hours mixing and feeling with her fingers.
at that age telephone was my big friend. i would be sitting next to dd but talking on the phone until she joined me or started pulling it.
at your sons age too i started the 'touch but not pick' rule.
and no my dd was one of those kids who didnt like dc/ps. she tolerated it because she knew we had no choice. but she was a mommy's girl and wanted to spend as much time with me. however we were doing a lot ourselves so she found being home much more fun.
i had a big tough computer or tv box. i put dd in there and then put in those air filled balls and a bunch of other things including scarves and handkerchieves that she could throw out. not only did she get to throw but she also got to understand how different objects fly.
easel and paint brush. i found a 3 x 6 table top and converted that into an easel for dd. then i got cheap newsprint from our newspaper office and giant paint brushes and water and let her go.
i think one key you need to also watch out for your son is he needs intellectual stimulation. if he is bored at the park show him things. like the wettish sand and the dry sand. the textures on the play structure.
when your dh goes for a walk with ds ask him to touch metal poles, the barks of trees... to pick up rocks, pebbles, twigs off the ground so your son can feel. and take longer to come home. show him shop signs. at that age my dd was a 'sign' fiend. she knew all the signs of cars and had touched and felt them. she also knew logos. that's the word. she loved logos.
does your city have a calendar of events happening. i took dd to a lot of free events. we also did light rail rides and bus rides for the fun of it. short ones.
a lot of her 'reading' material was my junk mail, kitty food cans, cereal boxes and smaller cans dd could use.
she wasnt a toys girl but prefered things from my pantry.
you know what i looooooved about dd being a HNs child is i was FORCED to look at the world differently. to discover what a treasure trove my house was. when i looked at a flour sifter it wasnt just a flour sifter. it was a cool toy.
the challenge crunchy mommy is you have to pretty much find ideas yourself. others are not really going to help you. that is why check into the out of sync activities books. it will give you tonnes of ideas.
btw where hunger and thirst is concerned even today my dd is like your son. she can say one minute i am not hungry and next moment wallop down everything.
also mama watch out for growth spurts. they usually follow a regular cycle. i think i became aware of it when dd was 3 but it happens at the same time - during summer and by end august and early sept dd suddenly shoots up. that takes a lot of energy and makes her v. grumpy and hard to handle and less sleep and emotional and always hungry.
last HAH!!!!!! you DO have a HNs child. esp. since you question your parenting. lady that aint the easy answer.
just look at what you have on your plate. a hard child. a job. the house. and not a really helpful dh. excuse me mama but the last i heard, even though society IS heading in that direction, parenting was not meant to be done alone.
do you know there are cultures where stranger anxiety does not even exist. their kids dont ever get separation anxiety?