Answer: Most pitchers don’t have the flexibility to open up the front leg/foot into foot plant without some amount of hip rotation so it is likely that your hips should be facing somewhere between 3B and home plate.
Answer: It takes lots of reps to change a habit or ingrained movement pattern. This poses a problem for pitchers who can’t throw that many pitches. So the use of drills/shadow work is appropriate. Also, it can be difficult to change more than one habit/pattern at a time. In order to increase your chances of successfully making the changes you desire, I suggest the following: (1) Work on one element of your delivery at a time, (2) Work on the earliest element of your delivery first, (3) Alternate drill/shadow work with live pitching to help take what you practice in the drills/shadow work to the mound, (4) Be aware that what you change early in the delivery will likely change (hopefully improve) things later in your delivery.
One more thing, leading with your hip can affect your timing and timing changes can certainly affect health in addition to velocity. Improvements to timing ought to improve health.