It's going to be ok.
Your initial suspicion was on the money, you overcarbed the bejesus out of that keg with the 30psi for 3 days trick. To tame the beast you need to disconnect the gas feed and keep burping the keg every chance you get for a couple of days. Then put the keg on gas long enough to do a test pour. If it's still too foamy, shut the gas back off and continue with the burping regimen.
Also, if you notice large pockets of gas in the beer lines after they've been sitting for awhile, you may have enough temperature stratification that the lines are significantly warmer than the beer at the bottom of the kegs. A small dc fan running 24/7 will keep the air moving enough to make that a non-problem...