I'm also syringe-feeding a sick pig right now. I'm using a 1CC syringe and cut the tip off and am feeding critical care. Yes, the 12CC syringe is way too big. Make sure you are only depressing the syringing when he is chewing (hence, swallowing), otherwise the food can get into his lungs. When I'm feeding my pig, I have him at an angle (not flat on his back) which also helps prevent fluid getting into the lungs.
Also very important is to make sure your pigs are not getting dehydrated. You can get a sub-cue done (an injection of saline under the skin) if it's too hard to get enough fluids in by the syringe method.
I don't know how often you are feeding them, but it's better to feed them small quantities more often, 6 feedings a day at least. I'm not sure if they can get dehydrated when they only get fluids every 4 hours so I'm going to see if I can get a sub-cue done on my pig every 24 hours.
You can syringe your pig 1/2 poop from a healthy pig to help restock the intestinal bacteria. Also, acidopholus power, I've heard is good.
Also, there are some injections to increase your pig's appetite. I've heard vitamin B is good for that, but I'm not sure because I'm still doing the research for my own pig.