You can only parallel 2 coils. They have to be in phase, which is a pair that were in series.
It may not be possible because of the winding and how the magnets were installed.
Feel how easy it spins when the coils are not connected. If it gets any harder with the coils connected, you either have the wrong coils (probably feels like heavy drag), one is reversed (turns very stiff), or the magnets are making them a bit stiff they may be out of phase.
I think I would use them separately anyway. Less issues with circulating currents.
Might be worth while to feed that 115VAC to a 12V transformer, then rectify to DC.
Direct rectification will result in a high DC voltage, and that's considered not good.
I do not think 'grounding' anything is a good idea in this situation. If there is a good way to do it, I can't think of it right now.
If there is a good reason to do it, I can't think of it either.
Maybe someone else will chine in.