I think 3 days @ 30 psi is going to likely overcarb it alright (assuming it's cold the whole time). I get mine where I like it in about half that time. If it is overcarbed, turn off the gas and purge the headspace. Then CO2 will come out of solution and equalize at some point less than it was before. This may take a few hours. If it's still too high, repeat. Once it's at a level you like, turn the gas back on at serving pressure and enjoy.
Foam problems can also be due to short lines, dirty tap, not opening tap completely, etc., but I'm pretty sure you're overcarbed.
I like a little more beer in my beer.