My great sympathies to you for your suffering with such an evil, difficult disease.
Here are a couple of tips that have been very effective in coping with gastroparesis.
Ginger capsules are very effective at compelling the stomach to empty. This solution works 85% of the time. If one has hypoglycemia from diabetes and gastroparesis, using ginger capsules with apple juice can literally save one's life. Great success compelling gastric emptying can be had with 3 capsules of Nature's Way Ginger Root, available at:
King Soopers grocery store (probably Kroger too)
http://www.vitacost.com/natures-way-ginger-root-550-mg-180-vegetable-capsules-1
http://www.naturesway.com/Product-Catalog/Ginger-Root-180-Caps
Everyone is different, so you may need to increase or decrease the dose of ginger.
Eat at least 3 grams of fiber before you begin your meal. Be sure to drink at least 8 fluid ounces (237 ml) of liquid containing water with your meal. For many people with gastroparesis, fiber helps move the food into and through your intestine. A very good choice in fiber supplements is Vitacost Friendly Fiber, available at:
http://www.vitacost.com/vitacost-friendly-fiber
Using fiber does not work for everybody, and you may need to increase your dose. For some people with gastroparesis, eating fiber delays gastric emptying. You will not know which group you are in until you test this for yourself.
I do not make any money from these suggestions, nor do I have any financial affiliation with the companies or products mentioned herein.
Thr smell is due to food stickign around in your stomach for too long, essentially putrefying. Unfortunately, it's one of the side effects of gastroparesis. (People with GERD and dyspepsia also often get this.)
Are you on any medications for your gastroparesis? If they're for motility (reglan, domperidone), then they should help somewhat with this. However, you can help it by eating a easier to digest diet: stay away from heavy meats (pork, beef) and fats; try not to mix too many food groups together (particularly fibers), and see about switching to some liquid supplementation, particularly in the evenings. (Ensure is your friend.) The point is try to eat food that will not stick around in your stomach too long.
In addition to this, keep a pack of gum with you at all times. It'll help cover up any bad odors.
Good luck.