OK, here's how you do this:
the built-in reverb of the board is fine, just use that (set the board to "dual mode" with that little recessed button, for reverb on aux 5 and delays on aux 6).
use your rack thing just for delay, by running the aux 6 out into the delay unit then the delay unit out into channel 16. set the delay unit itself for all delay, no dry signal at all.
the idea is you'll mostly set the reverb (for drums and acoustic instruments) and leave it alone, while the delay will be used on vocals (bring up aux 6 on each vocal channel) and you'll want to adjust the delay time from the rack unit front panel, and turn it up or down depending on the song or even shut it off between songs by working the ch16 fader.
as for that comp, it's a nice unit if you run it right.
don't run the whole mix through it, that's stupid, the whole band will get louder and quieter if the singer belts a hard note or not.
here's the trick for compressing vox on a 'wiz (the best thing you can do with it): pan all your vocals all the way over to one side, pan everything else all the way over to the other side, use an "insert cable" to put the compressor into the "L-R main insert" on the same side the vocals are on, then use the mono out to go to the PA.
this way that nice 160 is used to smooth out the vocals like it excels at, while not squashing the instruments and not affecting the monitor aux mixes.