I water my Starfish and Samurai Sanseverias every other week or so as well, but I'm also in a pretty dry climate. The fact that you are still getting root rot suggests that in your conditions, every other week is still too much! I know many people water their Sanseverias as little as once a month.
The pups on my Starfish have remained connected to the parent seemingly indefinitely until I physically cut them off, and they often don't have much root of their own until they're about the size of yours. After I separate them, I just stick them in succulent mix and water about the same as the parent (bottom water, if possible). They will take a long time to root and grow independently -- like 2-3 months -- and get creased/deflated some before they do, so patience is required. As long as there's no actual rot, they'll come around eventually!
I would also ditch the orchid mix and just use a succulent potting mix with some pumice or perlite added instead. The bark used in orchid mixes is pretty acidic and that might be part of the problem. In any case it's not typically added to succulent potting mixes and it couldn't hurt to get rid of it.
