The way I read, and understood the Shardstorm ability was that yes it recalls all previously spent shards, but also every shard on its body flies out and spins around the body (an orbit need not be slow, we have satellites that travel around the Earth very rapidly), hence always doing 4d4 no matter how many shards are returning. This also gives it a good self-defence mechanism should it be suddenly surrounded, which I really like.
The Lodeshard Control is fun, easy and makes sense but I agree with Asgetrion and feel it needs a bonus based on the number of shards.
Honestly I fell in love with this creature immediately when I saw it last round, but I like how you've re-envisioned it even more. I honestly just feel like dropping it into one of my campaigns right now, just as a one off quick adventure night, for a touch of the bizarre and different!
Best of luck Matthew!