Tuttle,
My answer is from a standpoint of assuming that you are on the spectrum. If not, then disregard this completely. I would start a conversation with him, maybe invite him for coffee, or something where you can talk for a few minutes. Mention what your diagnosis is, and see how he reacts. Depending on his reaction you could say something lightheartedly along the lines of "A couple of the things you do remind me of me and some other folks on the spectrum I know. It's no big deal you know. Do you think you are?" This way he can tell you if he is, or he can ask what the things are he does, and if he doesn't know, it will give you a chance to explain it to him and he could possibly go find out.
I wasn't diagnosed until my early 40s and it was from a situation really similar to this one. I had younger teens at home at the time, but there were a couple of older teens next door. They would hang out with my kids and play video games. They sometimes brought friends. One of the regular friends they brought asked me one day "How did you learn to deal with being an Aspie so well?" I had never heard of Aspergers, let alone the term "Aspie". I told him no, I'm not from Aspen, where did he get that idea from, I can't even ski. He explained what he meant. He told me he is an Aspie. I asked what made him think that I had it, and he listed off a big ole laundry list of stuff, which I thought were simply my eccentricities. Then he started asking me other stuff like do I ever just get totally obsessed with a subject or an activity for months and want to do only that, then one day it's just gone. I said yes. He asked me about sensory issues that I had never mentioned. We talked about a lot of things when he would come over with the Sims boys. He would always find time to say he was coming upstairs for a coke or something and would talk to me. He eventually gave me the name of a Doctor and said what would it hurt to find out? I went. He was right. And it's really better to know, for me anyway.
It helps me to know because even though it doesn't change my emotions and my feelings about something, but I can logically know that I'm so upset over something trivial because of the AS. And other things. I imagine it's the relief that Epstein-Barr patients feel when they find out that they really do have something and they aren't just lazy like people may have accused them of being. Or Fibromyalga patients when they find out it's really something and not just all in their heads or they are complaining over nothing. It's real. I'm able to handle my emotional outbursts a lot better since my dx, well somewhat better, sometimes, if I can stop and remind myself that it's really not as important as I'm feeling that it is, it's simply that I am wired to think it is. That doesn't always work, but it does sometimes. Unless I get overwhelmed.
I think the biggest favor you could do for him is to talk to him and find out. Don't do it as bluntly as E did me though. He thought I knew. He said "How could you not know?" It was obvious to him, but I had never heard of it. The only thing I had ever seen or heard about Autism was "Rain Man". I talked with him a lot afterwards, and still keep in touch to this day. It was really nice to be able to talk to somebody about it, who understood. Lurking here long ago was nice too, but I think it's going to be nicer now that I've actually joined. I don't see E very often. He works a lot. I see his wife though. She's a special ed teacher and she sells Avon also, and she's my Avon lady. I see him three or four times a year around holidays when his friends who live next door are home. All those boys are grown and married now.
Frances