Based on Bazz's information there is at least the idea that full fractine could be used as some kind of scrying mirror. As for direct use of the shard in crafting something, you are confident it could be done, but the specifics are likely going to require more arcane research than you can do with available resources on the ship. Ashheart doesn't have any infusions that could leverage the power of the shard, as least not any I can think of
Every single one would be too busy selling popsicles, cool drinks, or renting a out beach chairs and umbrellas to actually go swimming. The ones not vending would be waddling around with metal detectors
How explosive is the Phlogiston. Create bonfire has a range of 60'. If we were to pass within 60' and I cast Create Bonfire what kind of damage would be done? Would we be hit too?
In the 2e rules any fire spell cast in the Phlogidton causes the explosion at the caster as point of origin, not sure how Create Bonfire will work as the fire doesn't come from you. But it is probably as big as a fireball.
Create Bonfire would, like any other fire based spell, recenter on the caster while in the flow. It is an unavoidable aspect of casting in the phlogiston.
Having actually now seen the Rastipede racial impact on speed, that may need to be adjusted. I am not sure I had taken the full implication of even just three triplings uses would be. Perhaps lower it to just doubling it? That feels closer to right.