Wouldn't say you're a total a-hole (well maybe), but certainly making way more out of this than is warranted.

The zip tie thing? Who cares. It's a triviality.

With regard to bag mishaps, you asked what's done to prevent future incidents and they gave you an accurate and truthful answer. They review metrics on this daily and have a CI process where individual departments get corrective measures as needed. What more could you want? That's the appropriate course of action. And to be honest it seems to work. Hell I primarily fly AA but I believe DL has the lowest lost bag metrics of the major domestic airlines.

Delta serves 200 million passengers a year. ~550k a day. ~23k per hour. 380 per minute. I'm sure well over a thousand just in the process of writing this reply. Can't expect them to make a personalized court case out of every small inconvenience.