Several years ago, when stepping over and into our tub was becoming a safety issue for us, we had the old tub (a very very old tub) removed and had Bathfitters install a shower tray and surround (even on the ceiling). It was pricey but oh so worth it. They put in grab bars and corner shelves. We love it and so do the cats.

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.

I want to reduce fall risks as we age / guests age. There should be a vertical grab bar where you enter a shower or tub so you don't have to reach across the tub to the tile wall. Based on really helpful comments below about glass, my thought is to scrap idea of a walk-in shower with glass on two sides. (@JospehCorlett you may win!) ** What are everyone's thoughts on this idea instead? ** Note, this tub will not be used for baths. We have another bathroom for that in our main apartment down the hall. This is primarily for guests and sometimes for us.: (1.) Have a low tub - current vintage reglazed or new as low as possible, with the widest tub floor space possible. Suggestions appreciated! (2) Shower head, adjustable handheld, and tub spout on the long wall nearer window, spraying towards sink. (3) Build wall between tub and a new sink as in pic below. Shower controls mid-height on this wall - no need to bend down or reach to far long wall to turn on water. (4) Vertical grab bar on new wall inside shower, horizontal grab bar on long wall at standing height. (5) Use shower curtain rod as in second pic below. U and L shaped vintage look ones too unsturdy. Pros: Entry grab bar, takes care of weird window issue complicated by glass, fewer NYC permits needed than converting from tub to walk in. Cons: Tiny area for new sink. Evens out: Lifting leg into tub isn't great for aging in place, but grab bar helps with that and if someone is super limited range of motion they can stay in an ADA accessible hotel! Real estate pic of a unit in our building with wall between vintage tub and sink. Real estate pic of another unit with sturdy looking ceiling shower rod, low looking tub. Forget glass shower panel.

I would absolutely want grab bars attached to the studs. Also I might even want additional grab bars installed so that they are accessible wherever one is in the shower including accessible when one is entering and exiting to help with balance. The reason why you want them attached to the studs is that they are there for a worst case scenario when someone has literally lost complete balance and is dead weight on the bar. Not having them in the studs might be find when they are used to assist a bit or to steady someone but there could be complete failure when they are being grabbed - especially if someone is larger/weighs more.