I think a very important thing for you to know (and most of us wish everybody could know) is that you can't separate "him" from "his autism" - they are one and the same, it's part of us is it's intrinsic to our personality and character.
For those of us who experience that repression (which is basically all of us who've managed to pass for typical until middle age, for certain) it's fundamentally part of masking...and most of us will never be able to switch that off entirely. I can certainly consciously and deliberately put a passionate show on - given enough examples in film and TV, and having watched my other half over the years, I can easily make it look the way NTs would recognise. I'm just eternally grateful that my other half is so comfortable with me after a couple of decades that I don't have to.
That's not to say that we can't modify some of our behaviours, but they're almost always going to be something we consciously think about first.
I don't see it as something to "heal from" - it's just a part of me. I would probably never have shown passion or intensity in the same way as NTs anyway, so my factory settings would just have resulted in a similar disconnect to the one you're experiencing with him now, just for different reasons.
Which is to say...he could probably learn to show passion in the way you'd recognise, but I'm not sure you'd want him to because it would likely just be another mask - he'd be doing it to make you feel happy, which I suspect is the wrong result. Stay with him long enough, though, and you'll begin to spot the signs that it's there. If he's anything like me, it'll be there in the way he begins to drop the mask when you're alone, or in the similarities between the way he talks about his special interests and the way he talks about his time with you, or in the frankly insane amount of time he'll spend researching the perfect Christmas present...
It's there. It just doesn't show the same way you'd expect it to.