A) Try a half tsp of energizer and nutrient
B) If you scale-down the sugar it should be like 2lbs. Try 1.5 just to make sure you don't stress out the yeast
C) Speaking of yeast. One packet of yeast is good for up to 6 gallons I think they say. So just put the whole thing in. Unless you're using bulk yeast, in which case just put the same in for one full batch. It wont hurt. You'll just give them more yeast cells to start with. Also, not everyone does this, but I do a starter by letting the yeast sit in some warm water with a tablespoon of sugar while I put everything else together. I find it helps to evenly distribute the yeast when I add it to the batch that way.