Quite a lot there to unpick.
Why are you using (sweet) food for punishment/reward? Do you think this is a good idea in the long run? I try to keep food and meal times as void of emotion as possible, obviously this is easier said than done when my 4yo has a pink ice-cream!!
Try not to make the first thing you say in the morning negative, doesn't mean you can't work on manners later in the day, but it's kind of sad to start the day like that.
You call him a 'dictator', but how many choices and decisions does he actually get to make in a day? You need to engineer the situation so that he has choices, but that every thing he does choose is satisfactory to you and safe. This way when you get to something where he absolutely doesn't get a say in he is a bit more chilled out.
Make sure you have a small collection of kids cups, plates, bowls, let him choose which one, whenever he eats out drink.
When you offer a drink give him a choice, it doesn't have to be a big list just 'milk, Apple juice, orange juice, water' is all I offer DD.
Let him choose what he wears. I regular take DD out and about in her party dress, sometimes fancy dress. I've never felt judged, but DD has made a lot of people smile.
DD is in a school playgroup/nursery class so in uniform 4 days a week, but she has a selection of different options (summer dress, skirt, shorts/ cardigan, logo school jumper, zip hoodie) so can have a bit of control.
On her day off school I look at the weather (and my bank balance) and give her a list of options for activity and let her choose.
If your car is safe enough you can give him the choice of having his car seat in the front or back.
DD gets to use kids YouTube where she is in control of what she watches (within reason).
None of these things really matter to you, but will give him some control over his life, and make him more compliant when you really need him to be.