A.H.
My 2nd dad had throat cancer, the cancer is gone but due to complications on that kind of surgery he couldn't swallow and lost ALOT of weight and was hospitalized with pneumonia from the food going down the wrong pipe. He eventually had to have a feeding tube (he gets it out this week!!Praise God!)He found Ensure and it wasn't tasty but he needed to not lose any more weight. He also found something made by Carnation that was tastier. A nutritionist is a must it sounds like, my dads helped him start slow and figured out what he had problems with. The feeding tube is also something his doctor should consider especially if its a significant amount of weight. I would get a second opinion too about the tube.
Well wishes for you and yours.