In terms of the practicalities of how to get them to eat, I found the Eva musby chapter and YouTube video specifically on this really useful - it's like a walkthrough of what to say in response to the challenges. We used to say things like "take the next mouthful love", "keep eating sweetheart" etc. in the early days she was distraught at the 'amount' of food, and we would say often things like "you can trust us, we know what you need". I would refuse to negotiate or even discuss food, weight etc. there were frequent conversations where she would just go round and round in a "but whyyyyyyyyy" circle, it was exhausting and in the end best to not engage with it beyond the first couple of times of explaining something.
Our meals did sometimes go on for a long time, and we just sort of let it, but always encouraging her to keep going. Eventually they got shorter. Our dd was really furious with us and wanted to be away from us in her own space, so that was a motivator for her, as she realised that the faster she ate the faster she could be rid of us. You can use any motivator you can think of. My dd was allowed one walk a day then and we used that as a carrot sometimes.
We watched tv during meals, and we had these in the living room on the sofa rather than at the table, so she could feel sort of relaxed and distracted. I was clear from the start that she would be eating what we gave her, no matter how long we had to sit and wait for it, and we would be lining up any additional meals behind that one if it took us into the next meal or snack time. I really did focus on giving her small portions, so fewer mouthfuls, but as high calories as possible. I found the highest calorie snack bars, sliced bread, icecream, yogurt etc and that was all that was in the house. This is probably not what the dietician will advise, but I read on another forum a mum who said 'if you have to drive through hell, drive fast' and that really stuck with me. Weight gain is really the main element to the first part of recovery, so it seemed most sensible to just get on with that as fast as possible, although it was horrible at the time.
Good to think about support for you now too. We don't have family close by, and I wish we did. We told friends too, and they were sympathetic, but I realised not many people really got what we were going through - I don't blame them, I would be the same. There were some days I felt a strong urge to get in my car and just keep driving as far away as I could. I wish there was someone else who could have taken over for a mealtime occasionally. Sounds like maybe your mum can help with this kind of thing.
It has taken its toll on us as a family and me in particular - I have really driven what we have done and fought to keep us on track. My dh would have given in many times but I wouldn't allow it. For example he would often say things like "she's eaten most of it - why don't we just let her stop eating now?" But I knew from this group that the voice in her head would have seen that as a victory and been strengthened by it, so I just couldn't let those kinds of things happen.
I have taken a sabbatical from work for a few months, I'm really worn down by it all and trying to work while supporting her to recover. I'm very lucky to be able to do that, not many people can. It's hard juggle, so if you can find support then take it. We did a BEAT course called developing dolphins which was a 6 week online course. We met other families there, and learned a lot. Your FBT practitioner will hopefully guide you with this.
Sounds like you're in a good place and ready for what's next. Everyone here is always ready to help too x