Does anyone have any suggestions?

I have no clue about the meds but I am just thinking about his new anatomy now. You said everything is hooked up "normal", but if his entire large intestine was removed there is no way to be anatomically normal in function.

What did the dr say to expect in regards to bowel movements? I am just thinking out loud here, completely uneducated about UC,lol. The small intestines is the area that food is liquified and the absorbtion of nutrients occurs. The large intestine is the area that the water is removed and things are prepared for a normal controled bowel movement. If you dont have the large intestine it would only make sense to me that constant soft stools would occur, since the location that absorbs most of the water is gone. I would imagine that the need to go an excessive number of times is related to the fact that the small intestines job is to quickly transport its cargo to the next area. Which in your fathers case is the exit verses the large intestine to have the water absorbed. The small intestine is also very narrow compared to the large intestine, so anything that is making its way along will get to the exit in small quantities, hence multiple times to let it all go.

Has he asked the dr about if increasing fiber intake would help? But then again you dont want to slow things down and risk a blockage in the small intestine which could certainly happen and make things much worse.

Sorry, I think I should go back to sleep, I am rambleing. I hope I didnt confuse you more, just something to think about. Sometimes it helps alittle bit to understand why something happens to work on a solution.