No such thing as "seems like" when it comes to temperature. Calibrate the thermometer in a glass filled with ice, then water. Thermometer should read 32 F. If the product is carbonated at 2.5 vols, 14 PSIG will be fine at 38F. The four feet of 3/16" line will give you 128 oz./min. flow. If you desire a slower flow, use five feet.
Normally, when you start with foam and then the beer clears, the temperature at the faucet/shank area is warmer and the beer is degassing in this area. Or, you temperature is incorrect, thus your pressure is incorrect.
Scott Zuhse, Instructor
Micro Matic Dispense Institute