Not sure if I missed it but presumably you are snogging a lot etc, and that feels good? Do you know him well enough to ask him whether he’s done anything sexual with anyone ever?
I wonder if you should look past the weekend, and see what that feels like to you.
If it’s a disaster, do you feel that you’re close enough to discuss it? Because if you don’t , you maybe shouldn’t be having sex yet. I wouldn’t say that if you were in your 20’s in the dating pond, and just enjoying yourself. But given that you have so much more going on now, you owe it to yourself not to get into something you can’t discuss like an adult.
If he had some odd ideas, do you feel open enough to ask if his main source of ideas is from porn, because life just isn’t like that?!
I agree about the potentially being autistic. (Oh, and ftr, the community I am involved in, we all describe it as being autistic, because it’s just different, not abnormal, like being British, or brunette, so I hope no one freaks about about my using the term).
I have now been married to someone for 20 years who it has finally occurred to me (and him) is autistic. As is often the case, children were diagnosed first. I’m not entirely sure that I don’t have traits myself, but we’re getting the kids settled, and then looking at our own lives/marriage.
He had slept with one person I as far as I know, and they were younger than him (as in, 20 to his 25) so not a virgin, but also pretty inexperienced.
When we first met, he was very keen to work on whatever needed doing to get it together, and it had it’s odd moments, but generally we got ourselves sorted pretty fast 
. In hindsight, I think some of his ideas (concerns about performance, not climaxing at the same time, being keen on the idea of me being shaved etc etc ) came from porn, but, I think I didn’t even take any of it personally, and told him we weren’t in a movie, and to bugger off with the shaving thing. I can imagine taking it all far more personally these days...
Unfortunately some issues have since arisen which I’m not going to put on here for general reading, but definitely based on his later start in sex, and I suspect the autism. But I really hope I’ll be brave enough to talk to him about it, because it has impacted everything.
Happy to PM if you want, but otherwise I guess I don’t see it as any different to you getting back out there after 5 years with your new mum body, and not a ton of recent experience yourself.
Everyone is a potential disaster, and the issues you have with him are less likely, I guess, to be mind games, or crap of that kind.
I think my one suggestion would be that if I was starting again now, at this age, with kids etc (and lord knows, that may still be in my future), I’d make sure that I had what I wanted right from the start. If you can’t ask for it now, when can you?
I hope it’s fantastic 
PS. I’ve spent so long writing this, you’ve probably come back with some really important bit of info that renders this pointless, but your post really leapt out at me, so I hope this helped 