Glad to hear that your family, home and tank is going to be ok.
As far as mixing water and salt, sometime si only mix it for 2-3 hours. But i do use a mag 9.5 to mix my salt. MIx it for an hour, check salinity. Mix it for another 30 min check salinity, mix additional 30 min and if the salinity is the same, i'd use it. Its going to be less damaging than the foul sump water getting in there. 1-2 hours if your in a pinch should be just fine (depending on your salt mixing pump size of course). Good luck!
