I never had any experience with an Indo Regal, but all of my Indian Ocean Regals are out and about all day long. They are good eaters after they're accustomed to eating food out of the water column.
I went through the same ordeal as everyone when I first got into them. Killed a couple in QT and trying to get it to feed. My best method I've found is to not do any QT but to keep the newly acquired regal in a large acclimation box and hang the box in the display. Drop different food in the box and if the fish don't eat it in a couple hours, it's time to take it out and try it again later. The fish is a curious animal. It will eventually peck at the food and realize it's edible. Now the most important part is to keep the fish until it eats food out of the water column. After a couple of weeks, release the fish into the display. Fin rots and white dots on the tail is quite common with newly acquired regal angelfish. All of mine has it. But after a couple of weeks of good diet, it'll go away.