Oh Hun I can so hear your desperation and as much as I can empathize (you have described my second son right down to a T) I sadly don't have any magic cure or fantastic tip that worked for us because sadly nothing did. He just got older and finally stopped fighting it so much.

I cant even remember what age he was when this started as that period of my life is very much a sleep deprived blur and I would go so far as to say looking back now I would imagine I was quite depressed too

I dont want to make light of your situation at all but I will say that my 20minute max sleeper dragged his sorry butt out of bed at 12.15pm today

I know (believe me I know) that the light at the end of your tunnel seems non existent right now but it is there Hun and this WILL NOT last forever. Be kind to yourself in the meantime and do what you can, rely on who you need too to help you manage this