Had to return 2 o2 cylinders, on my third one now, because the first two were too tight and wouldn't open, even the AirGas people couldn't open it, wtf to that..

Tried out the ozone machine on red Gatorade, it made it a misty white color after 1-2 min on 1 lpm (anything below 1/2 lpm didnt seem to make any bubbles or change color at all, wtf to that as well, I thought the ozone concentration would be higher, doesn't seem like it made any.

A lower flow rate will increase ozone concentration.  If it is not bubbling though then there is nothing coming out of the tube.

Then I tried it on tap water, made tap water taste great and sweet, but had to turn the machine off because my whole (tiny) apartment smelled like sweet air and my lungs felt weird, and I started coughing up mucus which I haven't done since last week because I was sick..

It takes quite a bit of ozone to cause coughing, but it is usually a dry, spasmatic cough.  Try using a deeper container and really fine diffusers such as the white plastic diffusers for aquariums.  Also keep the diffuser at the bottom of the container.  All these will help increase the reaction of ozone with the water so less escapes in to the air.  Also ozonate for 10-15 minutes.

The ozone machine and glass I was doing this in was on the floor, to keep it from my lungs, plus the stone diffuser was submerged in a tiny glass of water, I really didn't think so much ozone could escape from there.. maybe it's coming directly from leaks in the generator?

Not likely.  Most likely the ozone is bubbling out faster than it can react.  Again a deeper glass and a finer diffuser can help some.

Any way, my apartment air is very very pure due to 2 industrial hepa/uv air purifiers (not the gimmick ones), so I think whatever ozone leaked out was shot up high by the air purifier vacuum thingy, couldnt find much to react with in my air and thus irritated my lungs, but just a theory. (this all total was about 7 minutes of the machine on).

UV sterilizers also generate ozone.

its just too bad i cant open the windows because it's snowing outside

EDIT:
tried it on green grapes, it didnt seem to make much difference at all, i couldnt tell difference from taste, the texture was slimier but could still see white pesticide film on the grapes, and there was no layer on the surface of the water in the glass the bubbled ozone/grapes were in (i did this for 15 minutes).

A white film is not indicative of pesticides.  Organically grown grapes can also develop a powdery covering over the fruit.

To ozonate fruits and vegetables though rinse them first so they are moist.  Oxidizers require moisture.  Then place them in a bag and blow the ozone in the bag for 15-20 minutes.  Afterward make sure to let the surface of the fruits and vegetable air dry to reduce the regrowth of any microbes.

I'm pretty sure it's because the air stone bubbles are not contacting the grapes at all, just rising to the top missing the grapes next to it. Does it matter if the bubbles touch the fruit, or will the saturated ozone water disinfect them without the bubbles touching? Btw I was using icy water.

The ozone will still work even if the bubbles are not contacting them.  But the bagging method I mentioned above is much more efficient.

  May I ask:

1. what does the output 50ug/ml, for example, consist of?

If using pure oxygen as the starting gas the mix would be primarily oxygen with a small amount of ozone.

50ug of ozone for each ml of total output (ozone and oxygen)?

Yes.

2. Why when the oxygen input increases, the amount of the ozone output decreases? For example:
1 LPM yields 9.3 ug/ml, but 1/2 LPM yields 20.5ug/ml.

This is because the faster the oxygen flows past the electrodes there is less time for the oxygen to react with the corona.  With less oxygen being converted in to ozone the unreacted oxygen dilutes the ozone concentration.