In the case of the helium balloon why does it matter what is inside the balloon. Why can't the atmosphere just push down on the top surface of the balloon just like my hand could push down on the top surface of the balloon to push it down? Look, because of buoyancy, the heavier air underneath the balloon is pushing the balloon up right?
The atmosphere cannot push down on anything until something pushes into it to compress it.
The helium in the balloon expands into the atmosphere and creates this push against the atmosphere as it compresses and forces that compressed air back over the balloon and around it to SQUEEZE the balloon to try and crush it but it can't, because just like you in the bath with a soapy hand and a bar of soap, you try and squeeze it and what happens?
It's the same thing, except different energies applied.
I think your theory is both very wrong a very confusing. The mechanism here is pressure. The only way to understand how it can move something is with a helium balloon but in that case it is the heavier air underneath pushing the lighter air inside the helium balloon up. So if that the case, then it follows that in the case of something like a car, it is the heavier car pushing the air up, not the lighter air pushing the heavier car down.
The car isn't heavier. It is the fact the the car is using the road or ground to push against atmosphere pushing down on it's dense body, minus the air actually inside of it. The so called lighter air above is not so. The pressure is enormous.
We only exist in it because we are simply made up of matter that mostly equalises the pressure because we are made up of mostly water, so we can resist it without being crushed. We still feel the pressure but we don't realsie we are because we are used to it and are born into it.
This is a little example of being used to something.
Walk about nude. No problems, right?
Now put on bug heavy boots - socks - heavy jeans - heavy jumper and coat. Top that off with a hard hat and even a back pack with your lunch in. Add a phone and a lap top and some change, etc.
You feel a difference but after being in them for a short whle, you forget you have them on because your body has adapted.
Well that's us against nature. We adapted because we grew into it by nature and we cannot survive without it and struggle with only minor changes to it.
This is why you redefined what pressure means for your theory. You can't just switch it up and use the proper definition for buoyancy in the case of helium balloons and use a totally different definition for everything else.
I haven't. I use it to highlight what I'm saying and hope logic kicks in with people to see it that way.
Anyways this is somewhat unrelated, but I wanted you to try something:
Bear with me here. So you've seen many videos showing you how a feather and something like an iron ball would fall at the same rate in a vacuum right? You didn't believe these videos were honest but anyways, the point was that gravity works on the feather just as well as anything else as long as air resistance is removed. So another simple way that you can show this to yourself without having to worry about having a vacuum container is to use a book and a feather and instead of dropping the 2 side-by-side, you can drop them at the same time with the book directly underneath the feather so that the book shields the feather from air resistance. When you do this they drop together at the same rate. You can probably try this at home with things already available in your own house.
But the book is going to do the exact same thing. It's going to compress the air below it and send it around the book - up against thelower pressure created behind it and compressing back onto the book and feather, clamping the feather to the book. The only time it won't happen is if the book is dropped unevenly which will push the feather away.