I really don't think feed per rev is useful except for threading.
In addition, 0.3 mm per rev is rather coarse - OK maybe for ripping stuff off but not for a good finish.
For Mach3 the instruction you want is g95. On some other machines it is g99 (stupid committees). I can't see either in your example, although I can see g97. All that does is specify a constant speed spindle - which is the default anyhow.
Cheers
Roger