If you topped off too much then your OG would have been lower not higher. Probably should have been around 1.050, and there's no way to create extra specific gravity from that extract. So like I said, 1.080 can only be explained by a volume error or poor mixing/stratification.
They're color coded:
yellow = 17 PSI
red = 35 PSI
green = 65 PSI
gray = 100 PSI
The 4 and 8 liter oxebar kegs are only rated for 58 PSI, so the tapping head for those comes with a red PRV.
Williams Brewing lists the item as "Oxebar 20L Amber PET Keg & Pressure Fermenter Tank" and has the video...
Is this the kit? Are these the instructions? I think there really are only two ways to get a high OG with this kind of kit. One is to add too little water and the other is to not mix thoroughly enough. Assuming that your volume is correct I'd be pretty shocked if your OG really was that high...
No, the small ones take PCO38 caps and these are PCO1881. But they do not need a separate tapping head. A lid assembly with handles, QDs, 65 PSI PRV and floating diptube is included.
Seems like a pretty good deal. Kinda funny that I'm now considering these big ones after kvetching for a couple of years about when the small ones were going to be available in the US.
No there's no coming back. If it is oxidized it will only get worse. And you picked the style that is probably the most susceptible to oxidation of all. The first thing to go is hop aroma and flavor, and then it's downhill from there. There's plenty of good stuff on here about...
Search for "four-way side outlet tee" in the diameter and material you want. I found some 3/4" ones on Amazon right away, but they are not black and come in four- or ten-packs.
That should be fine
and so should that.
I'm not sure exactly what you mean by "prevent the beer from carbonating." As I said, I think your beer is carbonated just fine and the foam is CO2 coming out of the beer. If you switch to the correct beer line diameter and length the CO2 will stay in...
A great way to become more patient is to build up a pipeline. If you do a really good job of that, you'll have more filled kegs than you can fit in your kegerator and will start searching the threads for the best way to store uncarabonated beer. ;)
Beer line should be 3/16" or smaller, with the appropriate length to balance carbonation as indicated by @Yooper. Or use an online calculator. At 15 PSI you would need 145 feet of 5/16" beer line to balance the system. I'm going to go way out on a limb and guess that you have a bit less than...