I like the look of this mission, and the rules seem pretty clear to me. Good work!
I think there is a potential sticking point regarding new spore blooms and how they are placed. They need to be a set distance away (3D6+3"), sure, but who decides where they go? Is it the player with initiative? Both players? What if I think it should go "here" but my opponent wants to place it "over there?" What if there isn't an empty space that distance away and at least 6" from any other marker or model?