I plan on doing that amount of cards in the same sequence as my curriculum. Obviously, unless your curriculum moves stupidly slow, you'll still be doing Zanki biochem while you're in a completely different block because you're way ahead in your curriculum. That doesn't matter because you're preparing long term for step. All you have to do is make sure you finish Zanki before dedicated. The plus side is that when you're doing Zanki you'll be recalling the cards from 1 month or more ago with the added context from lecture, so it will be reinforced very strongly. The downside, if you could call it one, is that you won't be able to use Zanki to reinforce lecture material like you would if you were doing enough new cards/day to keep up with your curriculum. But that's where making your own cards or using other people's premade decks come in. Theoretically, doing it this way will allow you to do very well in class and on boards. Furthermore, your Zanki burden will be so much more manageable than someone doing Zanki at the pace of their curriculum.
To answer your other question, I probably shouldn't be saying this, but there's a new add on for postponing reviews. It's basically crack, lol. If you're not the type to be consistently consistent, it will screw you over.