First and foremost, I would seek medical attention for the bloating. It can be caused by many dietary related problems including lactose intolerance or other food allergies, kidney problems, digestive issues, etc. and encouraging the person so eat more may only make the problem worse.
Secondly, ramping up protein and calorie intake doesn't equate to meeting nutritional needs. Many essential nutrients are not available in high calorie and high protein foods.
If he is on palliative hospice care, you might suggest tube or IV feeding to provide balanced nutrition without having to deal with the taste and not being hungry issues. Otherwise, I would suggest the patient's oncologist provide a referral to a registered dietitian or certified nutritionist.