I think it is worth trying to separate how you feel about his behaviour from whether his behaviour is acceptable, if you can.
It sounds like (I have been here lots) you are struggling with the enormity of the ASD thing, and that you are seeing his behaviours as a kind of personal attack. Although you know it really isn't, it can be so hard to see that when you have the bruises (physical or emotional) to show.
The trouble is, it can send a confusing message. Do you want your DS to feel regret and sadness for his actions? Because that is a tall order for any 2.6 year old, let alone your DS who also has ASD.
Also, it is crucial for you to avoid the 'battles' of wills, because they will just make you feel like a failure.
So, focus on his behaviour, rather than how it makes you feel. It is not acceptable to hit people, either with things or our hands. Full stop. Doesn't matter how much it hurt mummy, or whether it made her sad. Too much to process. It is just not acceptable to do it.
WRT the fruit flakes, did you just take one, or did you ask him if you could have one? Perhaps better to ask for one, and then reinforce with "must share", or similar.
Again with the phone thing, rather than "DON'T do x", perhaps instead block his thrust of the phone at you, and say "gentle, DS. Is it my turn?" Positive modelling rather than negative. Because he was taking turns, which is positive. But he needs to learn that he can't dominate and control.
Please feel free to discard any or all of my observations - I am also just muddling through. But I know that sometimes it helps me just to look back and work out how the day got so bad, and I realise that I had allowed a battle to go on, when in fact I need to get strategies in place to prevent it.