23w stands for the power rating which is 23 watts.
A quick Google search turns up a lot of different powerheads with flowrates from 600gph-1200gph that have a power rating of 23w.
Without knowing the brand and model # it's kinda hard to tell you the exact flowrate.
Yes, you can reposition your PH to point at the surface.
It is actually recommended for better aeration to ripple the surface of your tank.
Unfortunately I can't tell you if it's going to make that much of a difference in the flowrate.
I do know that a partial blockage will reduce your flowrate

You could try either restricting the intake by wrapping-up part of the filter, or restricting the output with an adjustable tip.
As for bubbles... I don't know.
My fish seemed to get stressed and hide more when I used bubbles so I stopped, but that's just my possibly twisted perception.