Possible autism, 3 year old - experience and advice welcome!

My son is almost 3. He's an absolutely delightful little boy who has met all his milestones at the expected age, except for speech and language. I'm wondering whether he's displaying signs of autism and would love some other people's opinions, from their own experiences. I'm going to note down the behaviours that possibly signify autism, and those that don't. When I use the word concern, I mean signs that could imply autism. If he is autistic we have no issue with this and just want to get the right help and support in place, so I don't mean concerns in a negative way. Thank you in advance for any comments!

My concerns:

- Delayed speech and language. Understanding is good and can follow instructions. Has lots of words but struggles to form sentences. Can form some 5-6 word sentences but often doesn't do this. Also babbles a lot, in his own little language! When he does speak it's usually articulate and clear. 

- Flicks fingers a lot and sometimes shakes his head a lot. Did walk on tiptoes a little bit, but no longer does this, and did used to hand flap but rarely does this now. Sometimes spins around with a toy aeroplane or similar. He's almost 3. 

- Spins wheels on toy cars, spins propellors on you helicopters etc. Can play independently for quite some time, often wheeling a car around the floor. Can stare and and be quite engaged with a small detail on a toy.

- Struggling to grasp potty training. Can sometimes do it but doesn't tell us if he needs to go - success usually comes from us constantly putting him on the potty or toilet rather than him initiating it. Lots of accidents.

Areas I feel are not autistic:

- Great eye contact and responds to his name.

- Doesn't have repetitive interests or obsessions. Enjoys lots of different books, activities, toys etc. 

- Very affectionate with all family members including extended family. Loves cuddles and will instigate them and receive them frequently at home.

- Goes into nursery happily with no issues separating, and will happily go to other family members with no issues. Also no issues with change of routine or going to people's houses etc.

- No sensory issues with clothing, not a fussy eater.

- No signs of emotional dysregulation at all - largely content and chilled out, though can get usually grumpy especially when hungry!

- Very sociable with his siblings - lots of laughter and playing. Thoroughly enjoys their company and looks forward to them returning from school. Enjoys other kids coming to play, though plays alongside rather than with them really.

- Has learnt colours, can count, recognise numbers, and recognise some letter sounds. Can play games involving sorting shapes and colours etc. 

- Will do pretend play, ie at toddler groups will play with themed props etc. Likes hoovering the floor when i hoover, will play at the toy kitchen making food and sipping from toy cups etc. 

- Shows empathy to siblings if they're upset.

These are the things that come to mind. Nursery has not raised any concerns other than slow speech but we are due to have a meeting soon so I wonder if they'll raise anything then. I'd really love any advice, reassurance or suggestions from more experienced parents as to whether you feel there is anything to be concerned about. I flit between thinking he's definitely autistic to thinking he just has delayed speech and a few little quirky stims. All advice welcome - thank you!