Is he constipated, which may be possible by some symptoms you describe..nausea, vomiting, crap breath, appetite loss, and can be caused by some feeding formulas, dehydration, opioids, and other medications. Change the nutrition if it can be a cause of the problems. I also did not see an anti nausea medication mentioned, which may help. Water rinsing also helps mucus, sleeping on an incline, Mucinex, Robotusim, seltzer water rinse, papaya or pineapple juice, and meat tenderizer rinse mix in liquid, even the juices mentioned, helps cut the mucus. Good luck with everything.