Tygon tubing is a brand name of vinyl tubing which is utilized in the food & beverage as well as medical field. It can impart a plastic flavor if used in large amounts and big diameters. 3/16" carries so little beer per foot that it is a non-issue.
As to the air pocket in the line and the low pressure. Yes, many retail accounts are screwed up as well. They may have had the correct set up at one time but eventually a warm keg was delivered by the distributor and of course, due to degassing, foam.
Foam appears to come out of the faucet very fast. The natural inclination would be for the retailer to reduce the pressure and "control the foam". Unfortunately the end result is high pour cost due to waste and lost resale from customers not wanting to reorder a flat beer.
Scott Zuhse, Instructor
Micro Matic Dispense Institute