I've tried standing more square to the shot, more side on, putting the cue under each eye (I am left-eye dominant), as well as in between each eye.
Reality check.
It doesn’t matter where you stand, the center of the ball is located on the line between the apex and the ball base contact point.
You can walk around the ball and that core vertical always dissects the ball.
Adding a cue doesn’t change that.
The connectiing of two points is all that is needed to create a line.
Placing the cue so that the shaft to tip line points through that vertical center, is an example.
At issue here is whether the cue lies on the perspective line from the player to the ball center.
Standing facing the ball with your cue pointed at the center opposite your right side, more of the left side of the cue is visible than the right, regardless of eye dominance.
It’s a matter of where you are standing relative to the line.
Moving your head laterally to the right, the perspective changes as more of the right side of the cue becomes visible.
At one point the rounded sides of the shaft are equally visible and if you continue to move your head to the right, the amount of the right side is more visible as the left side is less visible.
The equally visible perspective is your benchmark for alignment directly down the cue line.
Holding that perspective between the cue and the eyes check to make sure the cue is still pointed at the core center.
If it is pointed to the right side of center your diagnosis was correct.
If not, then the cue delivery is the problem.
A slight curling of the back grip fingers through impact will move the butt ever so slightly to the left shifting the cue line to the right.
A simple test is to shoot a ball, corner to corner diagonally, and check if the cue ends up pointed in the pocket.
Once your eyes are aligned down the shaft, the next steps are to have the.elbow hinge hanging from the shoulder on the vertical plane through the ball center.
A vertical thumb and triggered forefinger throughout the stroke hold the cue on the hinge plane throughout.