I am so sorry for what your Uncle is suffering - having to deal with the cancer is bad enough - but to suffer the GERD on top of it - I am so sorry.
My main symptom of GERD is terrible burning pain from my stomach, up my esophogus, and into my throat - like your Uncle I suffer almost constantly. I too have lost over 20 pounds from the pain. I take Prevacid and Carafate and they help a little - does your Uncle take any medications for the GERD? I am having an endoscopy done next Friday so they can try and see what is going on. Has your Uncle had any testing?
I can eat the following (although there are times when every thing I put in my mouth burns and hurts).
Cold cereals with non-fat milk (Cinnamon Life mostly), white rice, sweet potatos, tuna (no mayo on it) - salad with non-fat dressing, plain biscuits, white meat turkey and chicken, low fat yogurt, egg whites, mozzarella cheese (all other cheese bothers me). The only seasoning I use is Mrs. Dash Table Blend - no onions, no tomatos, no garlic, no spicy ANYTHING, so fatty foods, no fried foods. I do make myself blended smoothies with vanilla soy milk, yogurt, fresh strawberries and peaches and honey and find these VERY SOOTHING on my throat and stomach.
I deal with the pain daily and many times it just overcomes me and I am almost unable to function normally - this makes me depressed and sometimes so overwhelmed - but your Uncle he has overcome SO MUCH - there is help out there for him for this - maybe he just needs to find the right diet and medication to help.
My hope is when they do the endoscopy they will see what is making this so bad for me and be able to fix it
I hope your Uncle finds relief SOON and how sweet of you to try and help him. God Bless