Yikes...if you're new to SH, I really recommend that you start with a SH only setup, get them situated, conditioned, and eating well for you, THEN consider adding tankmates.
As mentioned, SH can't compete for food. Also, sharing a tank with "fast movers" (esp. tangs) usually results in the SH hiding, and starving. A 55 gal is WAY too small for a blue tang, BTW (you might be able to keep one of the bristletooth tangs in a 4-foot tank like a 55 gal).
As for the eel...no-frickin'-way-in-h3ll will that work. SFE's get progressively aggressive as they grow, and IME, you'll begin to lose tankmates to their nocturnal foraging. This is worse because SH sleep super soundly and are prime dinner prospects. Trust me...I kept a SFE for 15 years, and I've seen it first hand in a reef setup. So much so, that I eventually had to keep the eel on its own.
Nobody has even mentioned that SH need to be kept at cooler temps (<74*F) for best results...
Sorry...don't mean to be a "nay-sayer", but it would suck for you to have a bad experience.