I admit that my understanding of some of these concepts like futures contracts is negligible, but it still seems bad if, say, 90% of all bit gold is generated by criminals at no cost to them, while regular people have to expend their own resources to create (or buy) bit gold.

The economics in this regard are the same as for gold. With gold only the most efficient gold mines can make a profit, so only those profitable operate -- nobody tries to mine all the gold in the world. With bit gold, only those with the most efficient processors and most spare time will be able to make a profit, so again there will just be a handful of a few powerful computers, or many small computers but just using the spare CPU cycles (like SETI@home), solving the mathematical puzzles to generate the bit gold.