I wouldn't be able to say no
Me neither.
But that is really easy for me to say because I was the lost and broken teenager/young adult in the child/parent equation. And I have a particularly easy going, highly focused, well behaved 18yo who hangs the moon for me.
Plus I know the step-father bit is setting off (my entirely projected) parental wants before child's needs alarm system. So I can't be rational or disapassionate about the context.
Is there any way you could get some appropriatly professional fresh eyes on the situation from all angles ?
While MN is amazingly helpful and and has helped me carry myself at my most broken through some really difficult times and circumstances, there is the potential for lay people to project emotionally all over your circs (not pointing that at Anyfucker despite quoting her above, she has probably helped more people on MN than any other individual poster in the site's history, including me, and tends to have a good eye for cutting through the chaff to the heart of the matter) and view them through a highly personal lens that may not be applicable to your detailed individual circumstances.
There is a lot at stake. You boy's future, you ability to live with the fall out of either choice, your relationship with your husband... that's Big Stakes + High Risk from my perspective.
It would be nice if that sort of support and advice came free and in a timely fashion via the state, but often it doesn't work that way. So I think I'd be inclined to go without an awful lot to scrape together the money to access private services if state funded options are not on the table in the necessary timespan.
Again, the above comes from a position of bias. My parents and their circle over estimated their ability to know what was best all round and understand what was being viewed through a self serving lens. I forgive them. It is very common human mid-step, to overestimate your own ability to navigate very complicated issues and situations when you have a dog in the hunt and want some peace from it all. But I haven't forgotten how much it cost me and the permanent marks it left on me. I think I was worth a second, more expert, opinion.
I believe my father would have died happier and my mother would be living better too, if they had done that rather than rely on their own not exactly unbiased perspectives to guide them at the time.
Because I wanted peace too. I was exhausted too. I was hurt and felt rejected and unvalued too. And as the youngest, least experienced person in the mix, I had even fewer tools than they did to untangle it all and make things better. Yet the onus was primarily placed on me to be able to climb Mount Everest, on my own, in ballet slippers and make things right.