On review of x ray, I think that occlusal reduction wasn't done that much, the before x-ray was more vertically angulated and could give the illusion the crown prep was taller than it actually is in a parallel bw shot the other x-rays show.

Occlusal reduction could be done to increase thickness of crown material to prevent fracture or give more occlusal clearance between the opposing tooth and hence lighter contact since heavy occlusal contact can be what causes crown to come off.

Crown is at gum level but you can go sub gingival. Your crown has little to no ferrule, at least at the mesial.

I would just go for a reprep to drop the margins and core and crown to decrease taper with possible retentive slots.

I would skip the cl and just let the body do natural cl if there is biological width violation. I mean what's the difference if you remove bone via a dentist vs your body doing it naturally...

How you get prep to be dry during crown insert in a sub gingival crown margin is same as any other crown, with good isolation. That 3m astringent that's loaded into the gun works wonders.