Well... Here's my $0.02 for what it's worth...
I dove with Capt Hook proper and they did sent a dive "supervisor" down on the Thunderbolt who reminded one buddy team in our group that her time had expired and it was time to go. This was at 13 minutes into the dive when we were all diving 30% and had plenty of air. Capt Morgan used to be an independant operator and has been highly recommended, but I'm not sure what his current status is as far as his association with Capt Hook's.
As far as diving Looe Key and the Busch, Underseas and Looe Key Dive Center both have big boats and take out a lot of divers. Underseas does the Busch but not on any schedule that I've been able to determine. They run 2-tank trips, morning and afternoon. Looe Key goes out to the wreck on Wednesdays and Saturdays. They do a 3-tank dive which is 1 on the wreck then 2 on the reef.
Innerspace and Wreckreation Charters (me) both run 6-pack boats and I'm sure they, as well as I, would be more than happy to tailor a trip based on what the divers want to do.
I've seen Paradise Divers boat out on the water, but I know just about nothing about their operation.
As far as nitrox is concerned, Underseas, Innerspace and I have nitrox, Looe Key does not unless it's a very new development.
On a final note... as much as I'd love to do a Thunderbolt/Busch/Reef trip, I haven't ever taken my boat to the Thunderbolt so I have no idea how to tie in to it, I know it's a sunken barrel, and I don't have the GPS coordinates although I'm sure I could get them. So, for the T-bolt, I'd recommend a Marathon operator and for the Busch and Looe Key, I'd recommend myself, but then again, I'm biased
Hope that helps!
Rachel