but the key is if the box is anchored well to the ceiling joists? Those two little screws will hold up quite a load if snugged up tight. I hate using that threaded hollow dowel unless its absolutely necessary.
If you want to use it, then run up the dowel with the house wires in it and test it so it fits nicely to the lamp base, then attach the wires, this will eliminate all that twisting for you.