With the faults, bear in mind that it is a one show only outfit.
When you put it on, does it look awesome? Really, that's the main thing. Yeah, it sucks that the shop have been so useless, but stressing about that will not aid your cause, which is to look stunning and be super-excited.
The lining on my dress didn't line up with the zipper (couldn't take it back to the shop though, cos made it myself!) but you couldn't tell from the outside, so I didn't stress about it.

So, for now, fix up anything that is visible from the outside, or will affect function (like seams coming apart, but do remember, you're unlikely to be running marathons or climbing trees in it) Later, give the shop some shocking reviews, write them a letter, use your anger to let them know that it wasn't good enough.

But in the mean time, just focus on your special day and looking fabulous. It's more important than any shop.