1. The current will draw more than 3A at Max. setting, it will be high demand for protected circuit.
But I would not recommend IMR battery.
2. The flicker did come from the circuit, not the bezel & body connection.
It does appear very short time, then gone. From time to time, not alway happen.
The O-ring is tight sealed between the bezel & body, have to pay a bit attention to push it back. Not the thread problem.
I would suggest to insert the battery inside the body before pushing the bezel back.
The battery would guide the wire not stick out and leave 1mm gap between bezel and the body. For more home of the battery.
If the flicker is not comfortable to you, the alterative choice would be 8x7135 driver (Max2.8A).