Are these red flags for 3 year old son?

Hello! I’m a little concerned about my 3 year old son (39 months) and am wondering if he might have some kind of ASD. It may be because I'm with him 24/7 at the moment (and I have a lot of thinking time!) but I thought I would see what other people think. Here are a list of things that I think (although I might be wrong) are a little unusual:


Obsessed with his little brother’s hand. Follows him around trying to hold it all the time. I know that sounds sweet, but it’s really annoying for his little brother and he doesn’t just hold it - he separates the fingers and just kind of fiddles with it, like it’s his own little comforter.
Not a big fan of loud noises - has always hated the hoover, although it isn’t all loud noises because he has no problem with the lawn mower and enjoys pretending to mow along side it.
Doesn’t like big groups of people he doesn’t know. Cries and wants to leave.
Can’t ride a bike even with training wheels. I wondered if this was a balance/coordination issue, but he has no issue with the scooter and is great at balance beams etc at Tumble Tots.
He has a really sensitive gag reflux and throws up quite easily. Things like his own bogeys, poo, and even a bowl of his little brother’s mushy food makes him heave.
Gets very upset if he falls over and if there’s a scrape, he's hysterical until I put his trousers back on so he can't see it.
Spins - not a lot, but he does enjoy it.
Kicks up a fuss if a tiny bit of water gets on his hand, or if his socks are not pulled up properly.
 
And here are some things about his behaviour which makes me think that I might be worrying about nothing:
 
Has an excellent vocabulary. Very chatty. No problem with abstract thinking, has empathy, and loves to makes up and invent games/stories. His imagination is insane!
Is very funny and silly.
Very cuddly and loving
Social, if he knows the children. Plays with children nicely at preschool. Has ‘best’ friends.
Good at sharing.
 
I just want to know - are these typical 3 year old traits, or could there be a few red flags here? I just don’t want to waste our GP/Health Advisor's time. Apologise if I have offended anyone who has a child with ASD. 
thanks so much!!!
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