My Brother Has Adenocarcenoma. He Has Completed Chemo And Radiation

My brother has adenocarcenoma. He has completed chemo and radiation simultaneously for 6 weeks. The oncologist reported the cancer responded significantly well to treatment. He has had a j-tube prior to treatment as an alternative source of food knowing radiation would make it difficult to swallow. He spits frequently clear thick saliva. He has no pain now and physicians say he can eat but hasn't since August. His surgery is postponed due to chest blood clots. He is stronger daily and only swallows teaspoons of liquids. Occasionally he coughs hard and I think it make him leery to swallow. My questions: Why does he have this clear thick saliva? Is there anything to do to thin it? Do you think his stomach is rejecting food since it has been 2-3 months since he has had food in it? Thank you for your thought in advance.