Anne I can't believe DD has been discharged at 74% WFH, if the local EDT can't help they should refer on.
Sirzy DS1&3 are the same, they don't have ARFID but have EDNOS and a medical condition requiring a high calorie/fat/protein diet, they have overnight feeds.
Bubbles small steps are more maintainable. A MH nurse once likened it to slow weight loss being more likely to be long term. Have you got medical needs tuition arranged, and applied for an EHCNA?
Elfton did you formally apply for an EHCP? Reapply and appeal if refused, the majority of appeals are upheld. The bar for an EHCNA is relatively low - a) has or may have SEN, and b) may need SEN provision to be made via an EHCP. DD meet the threshold. If you didn't formally apply and it was the school who told you DD wouldn't get an EHCP don't listen to them. Schools often incorrectly tell parents that, but parents go on to successfully apply themselves.
Dyslexia is often co-morbid with ASD and other neurodiversities. Things often unravel for girls in their teens as the demands increase and they struggle to mask and cope. You mention coping strategies for the suspected dyslexia, could the school refusal be because she's struggling with the increased demands of secondary.
To a point I think you do need to push DC. DC with MH difficulties often struggle to rationalise what is in their best interest, and as Runner posted, we have found once a DC's world shrinks if is much harder to expand it again. It is one of the reasons we make some things none negotiable, given the choice DS1 would never leave the house again. But you need to know when to stop pushing because continuing would be harmful, each child has their own tell tale signs of reaching the tipping point.