So, the way surprise is meant to work is that when the first stone is cast, so to speak, surprise is checked per creature; some may be, some may not be. Here's an example: you're creeping up on a goblin camp with your party, and you attempt to take out the two sentries first; all the other goblins are longing around half asleep, but the sentries are alert for danger. You successfully sneak up on the sentries, and get the drop on them, but your initial attack doesn't manage to kill them both quietly and one begins to shout. We now roll initiative: The two sentries were alert for danger and are ready to fight - they are not formally 'surprised'... however, they didn't see you and didn't raise the alarm before you struck, and so the napping goblins had no prior warning - they are all surprised. Your party, presumably, is not. There is no "Surprise Round" - initiative goes as normal as all characters roll into the order. Some goblins may go before your party members, for example, if they roll well. Characters are surprised, however, functionally miss their first turn, while characters that are not, do not. This generally means that even if some of the drowsing goblins would be very quick to react (high initiative roll), your party will still functionally get to act before they do, since they're lose their first turn to being surprised, while your party members won't.
To best capitalise on this, most parties that organise ambushes together tend to "Ready" actions along with each other to all act at once... but we don't have access tot he Ready action, so we can't set that up, which weakens our ability to ambush in the game overall.
It looks like they've made some efforts to neaten up surprise in the latest patch - I haven't, since this patch, had my other party members be surprised when I initiate an attack, so far. However, the rest of your points about this particular mess are all very true and worth giving attention to.
In particular, yes, initiating a combat situation should force all characters into forced turn based and the initiative order. If someone has gone off on their own, and the party is a long, long way away, there should be consequences for that, after all.
I must note a disagreement on actions:
Actions are not "stronger" bonus actions, and Bonus actions are not "lesser actions" they are different *kinds* of actions, and they are not compatible. There are legitimate balance reasons for why you cannot 'downgrade' an action into a bonus action, and I support those being properly observed and maintained.
I also have to disagree with "Delay Turn": They do need to give us the Ready action, certainly, but giving players the free reign to simply pick their own turn order (which that does - players just delay to go after each other until they are acting in the order they want, and all together as a block), basically just abolishes the entire concept and function of initiative, and defeats the purpose of rolling for it at all. It also end sup making things boring and repetitive much faster, because players settle into a preferred routine and don't have to adapt to interesting or unusual timing dynamics in their fights. It also allows for various mechanical abuses and exploits to do with concentration timing and class abilities.
For the rest, I certainly agree with the issues you point out and support more attention being given to them!
