Cracking grout lines.

Cracks with just one sponge wipe

Residues on the shower steps

Some grout lines turned dark on wet. Guessing only some are sealed.

The only thing I see that's installer error is the grout job. That's pretty crappy. As for the "stains" and so forth, they look like glaze defects, which probably should've been culled out and/ or used for cuts. As for the edge of the curb, a little cleaning with a utiolity knife should take care of that. Do you have enough tile ro replace the ones with the glaze defects in them? Although those need to be replaced, it should not be on the tile guy to supply the new tile, being the defects weren't due to something he did.

That's IF those are glaze defects, as I believe they are. You mght try taking a utility knife to that tile in the first pic. Believe me-- this is glazed porcelain-- you're not going to hurt it.

Bill gives great advice above. Question on the shower step--it does not look like they used any type of finished edge for the top piece. Was that intentional to have an unfinished edge exposed?

How should it suppose to work out for the curb? It has to have one side of the edge exposed. I touch it by hand and it feels smooth. That's fine with me as the edge has a similar color as the tile surface.

Some tile lines don't have bullnose available to them, but if this is the Dal tile I think it is, I DO believe bullnose IS available. I'd be curious why he didn't question you about this, but if you didn't give him bullnose, I understand why he did what he did (unless he's working for the place you bought your tile from).