Yes, light beer will freeze at about 30 degrees where regular beer freezes at about 28 degrees. What usually happens is the beer line will freeze, you can usually thaw the line and all will be fine. I have seen kegs freeze before though.
You can bleed off the excess pressure that builds up in the keg from handling by the pressure relief valve on the side of the tap. The foam comes from either too much pressure or slightly warm beer. I don't like warm beer and beer doesn't like to be warm either.
BTW, a 5 month old keg of Miller is a great laxative. The yeast will definitely loosen your stools.