Well, no angel is truly reef safe. It is a gamble, some are coral nippers and some are not. So far I have been lucky with my CB.
As for Tangs that would be suitable for your size tank I have had the best luck with yellow and purple as far as being ich resistant. Every other tang I have ever had seems to have had ich at on point or another.
With an 80g tank I would not suggest more than 1 tang. Your tank is unique and does provide adequate swimming room for a tang so you could probably get away with 2 different species I think anymore would be pushing it. Another thought would be a small school of 3 yellow tangs, but there are so many species of
SW fish that will be compatible with your setup I would not think you would want to double up on the same species.
When picking fish do not look at current size, but how big can they get. I have 7 fish in my 90g and it is a flurry of activity with the fish and other inverts.
HTH,