You don't want any type of grease on any of the threads at all. Thread locker is OK, but no grease. I used the screws that came with my batteries and bus bars. I've had no loosening of the screws and my batteries are in an RV trailer that sees some fairly rough roads.
A couple alternative solutions for your balance lead connection:
1. Put the washer in top of the ring terminal. That way the ring terminal won't deform into the bus bar slot.
2. Drill and tap a hole in the bus bar to fasten the ring terminal to. This is acceptable but not implemented by many.
The balance lead ring terminal should always be on top of the bus bar, never between the cell terminal and the bus bar.