Bauxite's seriously overrated and I've done major magma engineering without using it at all. You do not need it.
Magma flows so goddamn slowly on its own you'd have to be a moron to just pop a floodgate and sit around waiting for the magma to ooze through, anyway. Use pumps.
You can even use pumps made out of non-magma-safe materials like wood, as long as they're not receiving magma from a pump on a higher z-level, which would cause the magma to overflow under pressure onto the front square of the pump and set it on fire.
You need to put power into your pumps through the next z-level above or below; and if you choose above, be sure it's above the solid wall-like rear square of the pump and not the floor-like front square if your magma may be under pressure. This'll keep the magma from getting into your power system and burning axles.
If you have any kind of sourced water, you can easily run as many waterwheels as you've got the logs for. Otherwise you're going to have to endure the excruciating expense of filling your whole map with puny windmills.
It sounds like you cranked up the volcanism in your worldgen to get more magma. This destroys sedimentary layers when overdone. There is almost certainly no bauxite in your site, it sounds like your civ doesn't have access to any, and I wouldn't be surprised if there's none in your whole world.
You should ask your dwarven and human caravans for every kind of wood they offer at the highest priority, because you're going to need a lot, especially because without sedimentary layers you don't have any coal for steelmaking. (You're probably going to have trouble with flux, too.)