I backed that project, but I don’t have experience with 3D printing of any kind.
In answer to your second question, though, it’s in the FAQ on the Kickstarter page:
What do you do with the leftover resin after a print? Can it be reused?
There can be a fair amount of leftover resin that doesn’t get used during a print. To use the leftover resin you simply syphon the saltwater solution back into the top container so you can start your next print. If you need to switch resins you can syphon all the saltwater back up to the top container and then drain the leftover resin back into it’s container.
The technical specs for MakerJuice say that the resin is stable when kept in a closed container out of sunlight.
