I believe it's the same actor who played Vala's husband on the final 2 seasons of Stargate SG-1. And I agree that he and Nathan are similar looking.
While the miniseries stands very well alone, I'm one that hopes that they return to with with another miniseries. I think a series would water down the concept and wear it out, but a miniseries could keep and perhaps build on the mysticism. We assume that Peter Krause's character is now invulerable, but is he, and if so, are there 'side effects' he had to endure now as an object? Also, some hints into the event that created the lost room would be great.