I have a 30 percent func. gallbladder, could it cause me to feel like i am going to gag and get sick after eating?

Unlikely: I suspect there is another cause of your symptoms. There are numerous possibilities from peptic ulcers disease to celiac disease to food allergies or others. A gallbladder without gallstones rarely causes symptoms and if it does it usually associated with a much lower gallbladder ejection fraction.

Yes : Different surgeons use different cutoffs but less than 35% may mean there is an obstructive process (stone? Sludge? Spasm? Inflamation?) that is preventing ejection of bile and thus causing symptoms. But many different things can cause your symptoms, reflux, ulcer disease, intestinal disorders, esophageal disorders. You may want to see a surgeon to discuss.