If I got a DM from someone online listing a number of details they know about me which I hadn't specifically divulged myself, I'd be far more likely to call the police than to respond and converse with the sender. This is a very badly conceived idea, even if the motives are otherwise good. It is almost certainly going to ruin the potential for a friendship rather more than encourage it.
Far better to simply communicate the fact that his role and input in the group is greatly appreciated, and you respect his right to privacy, just in case your previous comment to him might lead him to suspect otherwise.
No harm in explaining briefly that being on the spectrum does cause some difficulty understanding boundaries sometimes, but you don't have any wish to disturb his participation in the group, particularly since you regard the group as friends.
Short, simple and avoiding any risk of escalating concern he might have. And, if done this way, still leaves the door open for him to communicate with you and feel safe in doing so.
Far better to simply communicate the fact that his role and input in the group is greatly appreciated, and you respect his right to privacy, just in case your previous comment to him might lead him to suspect otherwise.
No harm in explaining briefly that being on the spectrum does cause some difficulty understanding boundaries sometimes, but you don't have any wish to disturb his participation in the group, particularly since you regard the group as friends.
Short, simple and avoiding any risk of escalating concern he might have. And, if done this way, still leaves the door open for him to communicate with you and feel safe in doing so.