Lots.
I think you need a different chair for feeding - we used a tumble form when dd2 was tiny, but changed to a jinx giraffe around the same age as your wee man (you mentioned his name by the way, so you may want to message mnhq and aske them to remove it from your post, esp as a foster child?). The jinx was a little more upright (I know you can tilt and angle the tumbleform but in my opinion the jenx chairs allow an easier position for feeding bigger (not) toddlers. There are loads of different chairs, and depending on his specific requirements, the OT should be able to suggest something a little more age appropriate.
I found that the tumbleform exacerbated dd2's extension patterns and it wasn't great for her posturally (it was great when she was tiny, but by two she needed something else.). The jenx giraffe (there are loads in the range) has a table attachment too - also great if you are trying to get him involved, for sensory reasons or dissection or whatever!
The movement getting harder with effort is very common. Dd2 had intention tightening, and often, as her movements were getting more purposeful and she was fighting to control it, she would make very repetitive uncoordinated swings and attempts. it's very difficult as the harder they try to do something, the more difficult it is! She also went through a phase of mirrored movement, where she would try to do something with one hand and the other one would mirror the movement - this got tricky with feeding too! V messy!
When is his next OT appointment? I would definitely ask for a new assessment for a feeding chair. The tumbleform will be great for him learning to feed himself (or supported) with a bottle, but I think for 'meals' he might need something else.
Re the sleep - do you know why he is waking? Do you think he is suffering from painful spasms? Wanting to change position but unable to settle? Or genuinely suffering from a need for company, possibly due to some attachment issues or difficulties associated with any previous placements?
Sometimes children with very limited movement do benefit from a sleep system - it might be worth asking your OT or physio if they think he would be a candidate, and ask their advice. Dd2 still benefitted from being almost swaddled at that age - she needed to feel very secure or her Moro reflex would kick in - she even felt unsafe lying flat on her back if she wasn't able to feel some pressure on her limbs. We used a grobag (just a light one) and a further blanket. As an aside I have also know children with cp who benefit from a slighted weighted blanket, but again, discuss with OT.
If you think he might be waking from muscle spasms or pain, then it might be worth chatting to the gp or his paed. Has he ever had baclofen or similar? Likely to be a candidate for Botox on the future? He's a bit little, but it depends how certain you can be about the cause!
Later on, some children do get a melatonin prescription, but I think you are probably a long way off that.
The other thing I will mention, as it exactly the age where we had it with dd2, is bog standard night terrors. for six months, she screamed the house down during the night, every night. And then they went away. We went through the whole checklist of every plausible sn complaint, and it turned out to be a completely NT issue. it's so easy to assume that everything is connected to the disability, but sometimes, just sometimes, it isn't.
Night terrors are the pits. I would just grit your teeth and try to stay sane, if that seems likely. at two, we had no idea what was going in her head, and it seemed v likely that she would have a learning disability etc. it hadn't occurred to us that internally she was following a fairly normal development curve and so was hitting the 'beginning of imagination' and this was causing nightmares and all sorts... Hindsight is a wonderful thing.
Dd2 was a little ahead of your wee man. She finally got rid of her walking frame after yr r. In yr r she was verbal, but it was really hard work for anyone to understand her speech because of her dysarthria, so she was statemented for communication primarily. These days (for the love of god) she manages to convince the teachers to let her join the school choir. It's a tragedy. I'm all for inclusion, but there should be a limit. she loves to sing, but it is largely monotone, and she has little to no volume control . In all seriousness, I'm very proud of her, but we aren't going to be seeing her on X factor any time soon! At school concerts I never quite know whether to laugh or cry! Her nursery worker learned makaton, and I do believe that this really gave her the impetus to communicate. Her gross and fine motor was so impaired that this seemed a bizarre thing for st to choose, but we had been through Big Mac and little Mac, and it seemed plausible, so we have it a go. It was a long time before she tried it herself, and it took longer for us to be able to grasp her approximations of the signs, but there are all sorts of methods that might work out.
What are SLT suggesting you use to communicate currently? Is he able to gesticulate for PECs or similar?
I do talk a lot. Sorry!
Do check out our cp support thread, by the way. Lots of mums with littlies on there too! It's somewhere on the sn children board, I will try and bump it...