Hi Aussie, a few months back i was getting those calf cramps nearly every night, until Wings told me about magnesium & calcium, i got a bottle of " Herron Magnesium Plus " especially made for cramps, i got mine in Safeway and i take one every night, i haven't had a calf cramp since.
I haven't had any muscle twitching and I have no idea if it has anything to do with the PN or not, but mine is small fibre damage as well.
Brian