I think pretty much every "beer line calculator" assumes 3/16" ID beer line has an internal resistance equivalent to 2.7-3 psi/foot. The problem is line resistance is dependent on volume and velocity - and I suspect wherever those resistance numbers came from they were based on much higher volume and/or velocity than seen in the typical home serving system.
Bottom line, having gone through everything you're going through a couple of years ago and having to replace my original 6 foot calculator-derived lines, I recommend starting with 1 foot of 3/16" ID barrier beer line per psi of serving pressure.
Give newly installed line plenty of time to get as cold as your fridge/freezer before trying a test pour. If your pours are excessively slow with no sign of CO2 break-out, you can try shortening the line by a foot at a time until you're happy. The trick is to stop cutting one foot before the break-out starts