You say that you read all the info about line length and gassing methods and yet you don't know what temp the beer is at.
You NEED to know what temp the beer is at before you can use the spreadsheets floating around to work out line length and gas pressure!
I am going to take a stab in the dark and guess you don't have any temp control on your keg fridge. So you likely have a temp of 4C at the most, all the fridges used in my brewery easily get down below 0C.
A bit of basic physics/chemistry - the lower the temp, the more gas will dissolve in a liquid.
Hence, you NEED to know the temp of your beer otherwise its likely you will make beer snow cones.
How did you carb the beer? Did you prime the keg with sugar (if so, what amount did you use) or force carb (method? time? pressure?).
EDIT - the 3m of beer line, is that 1 piece or does it have joins in it?