That looks good. Let's just drop the ? on the CR and turn the "X" for the sporocarp drying time into 1d10 rounds. Then it's done!
I'm not convinced that Protiston would really want to waste time during combat transforming into a sporocarp. I guess I'd be inclined to make the drying time more like an hour and have it happen between encounters. If you really want it to be useful in combat, let's go for 1d6 rounds. I'll let you choose.
2d6 minutes sounds fine. All done with Protiston and therefore this thread?
Woohoo!