Congratulations. Your Dad is on his way to recovery. My husband also suffered from hiccups although, they came intermittently, only. He made sure to walk around although, slowly, working up to a little bit more often as time went on. While coughing he made sure to hold a pillow against his tummy and a light sedative helped him sleep a bit better. I assume that your Dad is taking some pain medication which may cause constipation something, we solved with the use of stool softeners about 1/2 before intake of his meals. As Lainy has mentioned, an anti-acid may help prevent the long bouts of the hiccups.
I am wishing for his recovery continues to be a speedy as it has shown to be already.
Best wishes,
Marion