Poor thing. It is a lot to process and not the best way to find out without being told properly. I'm sure he'll get to a positive place in the end.
Here are a couple of good links from ANW to start him off:
autisticnotweird.com/growing-up-autistic-advice-for-teenagers-with-asperger-syndrome-or-mild-autism/
autisticnotweird.com/book/
And by the way his "1 in 100" estimate is already a bit outdated. In the US 1 in 54 children are diagnosed with autism and 1 in 6 with some form of developmental disability (see www.cdc.gov/ncbddd/autism/data.html). There's no reason to think the true proportion is lower here - and in fact in recent years the rate of diagnosis seems to be constantly increasing, so it seems quite likely to me that the true underlying incidence is even higher than 1 in 50. That means there are well over a million autistic people in the UK alone.
He might also like to know about famous autistic people (including Chris Packham, as @landofgiants mentioned above) in different fields, just to see the true diversity of autistic people (unsurprisingly, but maybe will help him feel nothing is closed off to him). If he likes vehicles then look into Guy Martin, for music Ladyhawke or Gary Newman, many scientists and computer scientists (e.g. Satosh Tajiri or lots of people say Bill Gates is autistic though I don't think he's ever said he is), for acting Dan Ayckroyd, Darryl Hannah, Paddy Considine, Anthony Hopkins, many many writers, many comedians (turns out seeing the world differently is very useful for comedy), for sport Jessica Jane Applegate or Clay Marzo, for business Michael Burry or Charlotte Valeur. There are autistic police officers, artists, lawyers, teachers, psychologists, cinema workers (just to name occupations I can think of for autistic people I follow online).