So my tank is 185g total inclusing sump. I'm thinking about 225/250 lbs of live rock, correct?. How much of this should I purchase as live rock and the other as base/dead rock?
Depends how much $ and time you have to let the dead rock fully cure. If you have 2-3 months before you are thinking of putting anything alive in the tank, then I would suggest something like a 20% live / 80% dead, but if your in a hurry and want to put fish in within a month I would go 75% live / 25% dead.
Live rock should already be "cured", that is the Live part of it. Yes, you want to stick the live in with the dead stuff right away to get the live seeding the dead as soon as possible to make it live.. it takes time though, depending on the ration of live/dead it can take several months before ALL the rock is live and ready to handle a bio-load.