OMG what a trial for your father, all you can do now is look forward.
When they removed the gallbladder the common bile duct should have been checked for possible obstruction. A small stone in the bile ducts can interfere with the pancreas and produce the symptoms and blood-works you describe.
About 40% of gallbladder surgery is ineffective; the symptoms returning in a year or two.
A short programme of liver-flushes may help but this can also deplete the bile salt pool which may be an issue. A good quality bile salt supplement may also be beneficial.