The sandbed is deep enough. You might consider putting your live rock in a horseshoe shape and put the anemone in the geometric middle of the tank. It won't outgrow your tank so quickly if you start him in the middle, but it will probably out grow your tank.
Haddonis don't need a ton of water movement. The Mag 7 and MJ 600 should be enough. If you can put the MJ on a timer to go on and off every 30 seconds or so that would be better than just a constant stream. Make sure you cover the MJ intake screen with a sponge. Haddonis have been know to wander into powerheads.
I have seen pink skunks in blue carpets and they look stunning, but there is no guarantee that they will accept a haddoni. Unfortunately, it just depend on the individual fish.
FWIW: Haddonis with longer, "looser" tentacles seem to be accepted more often by non-natural symbionts than haddonis with short, dense tentacles, IME.
For example, check out my "red house". Unfortunately neither of these anemones are with us anymore, but the blue haddoni with longer, less dense tentalces was accepted almost immediately by percula and orange skunk clowns(not natural symbionts). The lime green anemone with short, dense tentacles was only accepted by naturally symbiotic clowns. IME, there may be two "forms" of haddoni, I haven't seen one form changing to the other over time, maybe others have. The two types of tentacles don't seem to be related to color.
