How long and what size is your beer line? You need at least 6' and prob more of 3/16" ID line (I'd start at 10' and then cut it back if needed).
If you just want a beer without all the foam you should be able to vent most of the pressure out of the keg and pour at low pressure. It wastes CO2 gas but I get the feeling you'd just like to get a good pour at this point. If your beer line is too short (or too large ID) then you're gonna have
to serve at low pressure until you get more beer line. The restriction in the beer line is what counters your serving pressure. The higher the serving pressure the more beer line you need (or smaller OD, whatever gets you more restriction) to prevent foaming.
When you force carb your beer it will equalize at a certain pressure (eventually it will equalize at whatever pressure you set the regulator to). So if your beer has equalized at say 12 psi @ 40 degrees, then the reg won't flow unless it's set at >12 psi (or you pour a pint in which case the gas replaces the liquid you just removed). Now, you said you vented the keg so you should get flow at 12 psi until the keg reaches 12 psi. If not then I'm not sure why.
Even with kegging you need to have some patience. I don't really care for the 'set the reg to 30 psi and shake the keg' routine. I just set the reg to serving pressure (~12 psi) and wait 3 weeks, longer if possible (it takes a full 18 days or so to equalize). If you want to speed up the carb process, that 30 psi process works but I would just try to speed it up a little, don't try to carb a keg in a day or two, imo of course. It's possible you over-carbed the beer but I can't say for sure. If you did over carb it then you'll have to vent the keg every 8 hours or so until it comes down (there are other ways but this is the easiest I know of, you can also gently agitate the keg after you vent it each time).
Once you get a system down it will
be easier than bottling, I promise.