True, I've had cockerels crow earlier than 10 weeks. So, scratch the 10-12 week suggestion. Listen for crows, watch combs and wattles, eventually look for hackle and saddle feathers. Or, post pics on BYC, ask others, and get 20 different answers (even if pullet or cockerel are your only options).
I hope your baby pulls through, the others have made wonderful suggestions on caring for it, I would do the towel in a circle to offer it support for it's little head, I bought all pullets when I first got chickens, even then it's not a 100% guarantee that you will get all hens, I've since hatched my own and dug around the internet looking for ways to tell beyond waiting for them to crow or lay, I watched a couple of videos that people had made that showed using the wing method, I've been told it doesn't work for all breeds (mine are mutts) but it's the long short, long short for hens and the straight across for the feathers on the roo's. Done within the first week of life.
Honestly, I wouldn't mess with a vet. The office call alone will be very expensive. It's also hard to find a vet that will even look at a chicken. I think you're doing the best you can for it right now. Make sure it has a source of heat to keep it warm, but not too hot. Keep water and feed available. Keep it comfortable. If you can get ahold of some vitamins or electrolytes tomorrow, then do so. If not, just keep doing what you're doing.
Gatorade is not a bad idea. The electrolytes are a good thing to add. Have you got some Chick Saver or even some Pedialyte? Either one of those, added to the water, should help, as well. As long as your baby is warm and drinking, there's hope. As fragile as they are, they often surprise us with their resilience!
