I would assume that you are using a barbed tailpiece and coupling with that shank like these:
the above tail piece and winged coupling require a gasket like this:
I'm pretty sure you have that stuff hooked up correctly. I think it would be leaking badly if you don't have the gasket installed.
So, it appears that you have everything connected properly, the tower and tap is cooled OK and the beer line is the right type. About the only thing left is the possibility that the beer is over-carbonated. Frequently, over-carbed beer will foam like crazy when you pour it, but little CO2 is retained and it will appear more or less flat in the glass. I'm not sure why this happens, but it does. You would think that only the excess CO2 would be released with the foam, but that's not what happens. I think it's because when the beer is all foamy, it does release most of the CO2 very quickly and when it settles down there is very little gas left in solution. So, I would try to rid the beer of the excess CO2. You can do this by repeatedly releasing the gas through the pressure relief valve and shaking the keg between releases. This may take a while to do. Wait for the beer to settle down a few minutes between releases before sampling. Once you get it to the proper carbonation level, try pouring at slightly less pressure than storage pressure to reduce foaming for a few days until you can get everything balanced. Bring it up to the normal storage pressure (12-13 psi) at the end of the session. Also, be sure that the beer line is real beverage line and not just ordinary plastic tubing of some kind. I think you have the real thing judging by the dimensions you provided above for the tubing.
Bottom line: My conclusion is that it's an over-carbonation problem and nothing else but.