Hopefully some experts will be able to answer your questions. All I can do is tell you what I have heard, I am still very new with them.
Someone please correct any of these statement is they are wrong, they came from my LFS
Feeding: I was told once a week is plenty as they will get some of the food from your fish feedings also. You will know if it's not getting enough food when it becomes very pale and sickly looking. Hope to never see that condition! As to how to feed it i'm still learning. Right now I rinse off the frozen food to take the bite and fats off of it, and hand feed the anenome. I just hold it near its mouth area until it clings to a majority of the frozen food. (some of it floats out into the open water). I'm thinking about trying the Turkey Baster method instead, so I don't have to stick my whole arm in the tank. heh.
As for Carpet vs. BTA I'm not sure. I know that different types of clowns will pair with different types of Anenomes, and even that is not gauranteed. Carpets are a bit more money, although I personally liked the looks of my BTA over the Carpet. Matter of preference here. I got lucky and my clowns paired with it the day after I brought it home.
Looks like you have your water conditions right for the job. And make sure you have at least 3w/gallon, I think more is better. Mine has finally adapted to my lights, so you might want to acclimate him as mentioned above so you do not shock him.
Wish I had the tank size for the Hippo Tang, they are beautiful creatures! Good luck on what you decide, let us know!