Ok, you don't sound like a loon, but you do sound like you are overthinking everythin and over worrying, it's a bit like the grass is greener type mentality.
Your DS is not at a disadvantage to children with siblings, he just has different experiences, just like children with siblings have different experiences to onlies.
You need to stop worrying and thinking negatively about it.
I love the fact that I only have one child, makes for so much more of an easy life, especially on days out. I only have one DS to entertain, keep happy, feed, take to the loo, encourage to keep walking on long walks, get dressed, get undressed, ferry aorund, make sure he doesn't get lost etc etc etc
Seriously, think how much harder it must be to take three or four childrne to a theme park or play area or something?
Children make friends easily too, altohugh DS is an only he always just makes friends with other kids in parks, soft play, camp sites, or if he'd rather play alone, that's what he does,.