Just by looking at the material it appears to be heavy dense and abrasion resistant. This bag had the crap rubbed out of it and is suffering damage from heavy abrasion.
Does the material appear to be lighter weaker or less temperature resistant than other baggage materials? IF no, this is entirely related to it's handling
This is far more likely an airline issue not likely a bag issue, If you ware flaming ANYONE in this post please post up who you flew with and where you went. It's very likely the edge of this bag was rubbing or dragged for long distances either on a conveyor wedged in a manner where abnormal force was applied or drooping and rubbing the tire on a baggage handling cart. or dragged a long distance by some operator to produce that kind of damage.
As for repair. I suggest a bigass abrasion resistant patch sewn inside and outside. Use a bigass sewing maching with bigass thread.. Those guys at the shoe repair places at the mall are usually good dudes to hook you up for these kind of things for a low cost.
As for your shop and NP they should've hooked you up with at least this advice but you probably came at it similar to this post....blaming them and saying the bag was crap.....so they were less than helpful.......
Now if NP were a STELLAR company they would hook you up with at least a swatch of matching material to make it look stock after it's repaired. But alas that kind of customer service died long ago with the closure of hardware stores that were owned by your neighbor.....
I can mail you some big ass thread (sail repair thread) and you can sew it by hand if you're sew inclined.