Multiply the first equation by 5 then calculate the mass of the compounds using the balancing numbers as the mole number (via stoicheomtery). That should tell you how much mass is needed for each reaction to work I believe.
Can be done this way, although you can try to just balance the overall reaction and work with a single reaction, not two.
work out the moles of nitrogen needed to produce that much gas via molar gas equation
Not sure what you mean by molar gas equation, but yes, moles of nitrogen from the volume is the right starting point.
should get 7/6
No idea what these numbers are intended to be.