1 gram per gallon is hat i've read...that seems like just a pinch...i don't have a scale that exact and my local drug dealer isn't keen on farming out his equipment...
I use Wyeast nutrient. IIRC, its recommended rate is 1.1gm or 1/2 tsp per 5 gallons.
I got a 100/.01gm scale on eBay for about $15 shipped.
EDIT: 1/2, not 1/4.
Fermaid K is useful for >10% beers... The typical use is to add it along with a dose of additional O2 and some extra sugars for the yeast. For example this beer.