training scapular should train in a co-ordinated way, not just the single muscle.
impingement can be caused by scapular, humeral head, your thorax stiffness, best way to find which one is the cause is change it when you doing your painful movement, see which one making your movement better.
1. humeral head, pull your arm backwards with a theraband right around your girdle (close your armpit), then lift your arm up, or loop rubber around your hands, and pull hands apart, tension your posterior shoulder up, any change with pain during movement?
2. scapular, better movement is posterior, upwards to clear your humeral head. your rhomboids is working together with your trapezius and other rotator cuff muscles at same time to get your scapular move.
3. get thoracic more flexible, especially backwards (be careful not your lower back).
Sorry can't see your video either.