Very low pressure at the end of natural gas pipe
Your 2# regulator is likely dropping the pressure down to about 1/4 psi which is what most appliances need. By putting the tee after the regulator and running a 80ft line isn't going to be sufficient. Longer runs generally need larger piping. Your 1/2in line wont be able to keep up. You probably should have ran the 2psi line (i.e. a tee before the regulator) and installed a 2nd regulator up there.

Here in the United States, most houses are fed 1/4psi after the meter and if there is problems with piping or a need for large appliances, generally pressure can be increased to 2PSI.  Since you have 1/2" gas piping, that might explain why you have 2 PSI of gas. On my house, the line coming in is 1-1/4".