Yes exactly using pinky 0 on a right-handed numpad with your left keyboard is awful. The + and enter placement isn’t as bad for the thumb, but I still greatly prefer it on the left for use with the pinky or ring finger

Also this is an elaborate solution, but you could try something like it. I use the left half of a split ortholinear keyboard (Keebio FoldKB) for a lefty numpad with the 0 set to the spacebar 1.25u mod to the left of the spacebar. It works really well other than having 1u keys for + and enter (I use 2 for + and 1 for enter). A macropad also might fit you

Edit: edited “spacebar” to the mod next to it