Thank you all, you're really helping me move forward with what I need to do.
Any of the options wrt to friend and I marrying now, or him adopting my dc just now would have financial implications for me, and him. It's interesting to know that it wouldn't make a difference to SS allowing my dc to stay with him, that's helpful to know.
If I am to get a terminal diagnosis then that would change things significantly, and I can take a lump sum from my life insurance, which would stop most of the benefits anyway so I could move forward with getting friend legally involved as a step parent or Co parent.
I don't think adoption will ever be an option as my ex wouldn't let it, he wouldn't allow my dc to change names and I had to take that to court also, if he allowed adoption then he would never be able to tell everyone that I'm withholding his dc and alienated him and all the other lies he tells.
It's my fault he knows all of this, I was hoping if I told him the situation he would have some compassion, start seeing the kids more, get over his homophobia, and generally step up and be a parent. I knew deep down he never would, but I didn't think he would use it against me as he is.
His main objections to my friend caring for my dc is because he is homophobic (mixed in with him thinking we are shagging and him not wanting my dc to ever have a step dad).
Next week my will, and the wording of it will be my top priority, I'll have to have some hard conversations with eldest dd, but I think you're right that she should be in charge of that side of things then there will be no ex trying to gold dig, and she and my friend will sort it out between them, they are also very good friends and have cared for my dc together through my treatments and operations.
I was hoping not to put too much on her, but she would be really upset if she knew I was struggling to find a solution and didn't ask her in order for her to get on in life. She's truly a lovely, sensible girl, and she has been an angel.
Neither exh or I have any family (bar a few distant cousins and aunties) so none of them would be an option as they don't really know my dc at all. Friend has been there from day one, at least once a week, at the moment it's daily, so he knows the kids almost as well as I do.
I also have evidence of exh saying he wouldn't give my dd her medication for epilepsy, as well as him saying I have munchausen by proxy when she has been in hospital, and telling me it's my shitty genetics etc, he hates it that she has epilepsy and finds it embarrassing, so I would really worry about her health with him.
After I speak to a solicitor I will contact SS and see what can be put into place, I just floated the idea of friend registering as a Foster carer past him, and he said he would happily do that if it makes things easier should I become a lot more poorly, maybe that would be a better option actually as he would get a little more money from the state I think? There's absolutely no reason he wouldn't be accepted, no criminal record (bar shoplifting a Cadbury top deck from woolworths when we were 13 🤣) he's fit and healthy and has a good job, own house etc (although he would move into mine and rent his out should I die).
There's just so much to think about, and it's causing additional stress that ex is putting a spanner in the works out of spite when all he actually has to do is nothing, and leave me to make arrangements.