1. I usually do not account for the starter volume, at least not on paper. I do a starter most of the time, so now that I think about it, I think I unconsciously account for it...
2. Yeast Nutrient? meh. I think that's one of those things that sounds good on paper, but really it's not worth it. I've got a vial of it, I bought years ago, I'm not convinced it really winds up doing anything. If there is ever a place for it, it would be in an all grain batch (but I don't even use it in my AG batches...). Any LME/DME you buy is going to be fortified and make yeast nutrient quite unnecessary. I liken it to us taking a multivitamin. All other things normal and equal, not going to make much of a difference. But, in proper amounts, it won't hurt either... but if you put it in your starter, no way do you need to add it to the 5gallon batch too.
Primary: Imperial IPA, Biermuncher's OctoberFAST, Zombie Dust
Secondary: Caberlot (my first wine!)
Cold Crashing: Goat's Spare Tire
Kegged & On Tap: Bavarian Hefeweizen, 3-year aged Cider
Projects: The Ravens Keezer - Custom Gas System - 10gal MLT