The presumption is you overcarbed that keg of beer, hence you actually don't want to put any CO2 on the keg until you've tamed it by releasing the head space pressure every time you think of it over a day or two. After a day of that you can put low pressure on the keg to draw a pour to see how it's doing; if it's still foamy cut the CO2 again and keep popping the keg PRV (or the gas post poppet if no manual PRV) for another day and try again.
As for the beer line, you might be surprised how well PVC beer line will coil. I have 12' Bevlex-200 runs on all of my taps and I simply coiled the slack so it fits inside the keg rubbers and secured the coils with tie-wraps.
There are probably a thousand "beer line length calculators" in print and on the web. I'd guess 99.99% are copies of the original - which got it wrong from the jump. Hence the 5' lines that seems to be the default for dispensing kits.
If you want to understand why 5' really doesn't work well except under ideal conditions (low carb level, very cold temperature, no stratification or thermal gradients anywhere in the system) you might spend 10 minutes checking out the site of the only beer line length calculator work using...