claw, i agree with Satrlight, your ituation does sound extreme.
whereabouts in th ecountry are you? do you have any SN groups you can go to? (they won't cure anyhting, but don't underestimate the restorative powers of sitting in a room where the majority of people understand that fussy eating is not disliking peas!)
on the schools front, I'd ask the home educators what to do about de-registering if that is the way forward for you. they'll all know what to do.
I would not wait before applying for a statemnt. you have to write reams of stuff on how the situation is at home as evidence, and it will be a chane to get it al on record.
would you be up to (politely) calling the LA and talking it through with a case officer - along the lines of "ds doesn't eat at school. he is unable to. this is not acceptable. jhe needs support. ds is unable to ask for help with toiletting. this needs to be addressed. he needs support." etc, and going through all his needs? when they (inevitably) start wafflign about strategies to put inplace, try to pin them down a bit.
I do actually have a reasonably good case officer, who has agreed that dd1 wasn't getting the support that she needed (albeit in a roundabout way). Stating facts baldly often helps, I find. I described dd1's issues in minute detail "dd1 feels unable to use the toliet at school. she is dry at home. at school , she refuses to use the toilet, and will hold on all day. this results in either: dd1 refusing to drink so that she doen't need to go to the toilet, which is unacceptable and dangerous to her health, or dd1 holding on al day, which is unacceptable and dangerous to her health. in a year of attending school, school have been unable to address this issue. dd1 does not have this problem anywhere else, or with anyone else. the school is unsuitable"
,sprry to go on> and so on, for each problem with the school. once the issues are listed fully, it does become harder for the LA to state that your ds doesn't need a statement, or to claim that the school are coping.
on the IEP front - totally ridiculous! if your ds is on school action plus (fwiw), then surely the school themselves are stating he needs extra help? for him not to have an IEP is surely against COP? the school cannot have this both ways; if he needs extra help (thus action plus) they can't then turn around and say he needs no help!!!