(1) Would it look best to have the bullnose tile end exactly at the outside edge of the shower curb? Or would it be better for it go a little beyond, for example, have the regular tile end at the outside edge of the shower curb and then the bullnose tile (which is 3" wide) extend beyond? I'll usually end the tile flush with the FINISHED outside face of the curb, but I have, on occasion, gone a couple of inches past that the contractor's (or owner's) request. (2) If I have the bullnose tile end at the outside edge of the shower curb, then the grout joint between it and the regular wall tile will likely be running either under the shower door frame or along the edge of the frame inside the shower where caulk will be applied. Is this a big problem in either scenario? Nope.

I've been reading last few weeks on proper shower wall install since mine leaked bad enough that I'm tearing it down to the studs. House is only about 15 years old but, IMO, improperly built like so many other tract homes. I'm discovering It's greenboard with no vapor barrier or waterproofing of any kind. At first I thought leak was from cracking grout, then running around the prefab shower pan and exiting the front where the shower door and curb are since there is no flange. I siliconed the wall-pan interface 3 years ago when I discovered a small leak, also tried to seal various shower door channels. Now, 3 years later and wiser, I think the combination of wall and all those channels/panels of the shower door was the bigger problem. Silicone on the wall bottom only helped trap some of the water running behind the wall from coming out while any water on the shower curb went straight out the side to the floor. So I'm pretty much set on cement board and few coats of paint on waterproofing, reusing the plastic pan, but one thing I haven't seen addressed much is the shower door. I believe that is a big problem because any water that gets on the "threshold" channel may run straight into the wall and out the front, no matter how much waterproofing I have on the walls. And the only line of defense is silicone at the time of installation. I'm the kind of person that likes a physical barrier or redirection, not rely on cualk to keep water out. I feel no matter how well caulked, it's only a matter of time when water works its way to open up a gap since daily use by 2-3 people is a lot of use. It's not like I can check daily if there's water outside the shower. Everything is nicely hidden so I don't know failure until it's bad enough and there's evidence of damage. I think with the cement back/waterproofing paint I'm comfortable with the wall install, but how is a guy supposed to properly install a shower door and never worry about it? Sorry for the long read, but I wanted to give some rationale on why I'm concerned about the shower door instead when there's so much discussion on the wall/tile itself.

"What could cause this to happen?" It's more an issue with the hinge screws not being anchored to the wall framing versus the marble not being properly installed. With the weight and moment of the door pulling on the upper hinge, and with the hinges only being secured to the "marble slab", it caused the slab to separate from the wall. " How can it be fixed?" As has been discussed,if you can add blocking from behind, do it. Reset the slab so it's tight to the backer, then run longer hinge screws through the slab and into the framing. " Who should fix it?" Your GC from the original build is responsible for the details, or in this case, the lack thereof. He should have seen this coming. Ultimately, the GC is responsible for the failure. The guy who installed the marble, it's really not his worry. The glass installer, he should have known that screws set only in a wall slab would not be sufficient long term. The failure is on the GC and the glass guy, partially on the glass guy for not raising an objection. The repair? You'll want to hire someone new to install the blocking and repair the drywall. If your GC is still around, ring him up. Then have the glass guy back to properly anchor the hinges in to the new blocking.

Quite honestly, you have more problems there than the broken tiles. The install is not good at all. Spacing is uneven. it looks really bad. Have you been watching him and taking pictures? Did he even waterproof underneath? This in my opinion should be all torn off, and completely redone, with a tile person that actually knows how to tile.