Ebay..shipping... packaging...USPS...damage?

I bought 50 glass jars from eBay for $18 and paid $16 for shipping. Totaling $34. My package arrived today on my front porch, the box no long has corners and its bowed, too small of a box as well, one of those flimsy white ones. Nowhere on this box is a sticker or even handwritten "FRAGILE" or "GLASS". On my front porch are shards of glass everywhere... Not even large pieces (those are still in my unopened box). I can tell by the packaging that its the sellers fault for "improper packaging", I've contacted the seller and waiting on a response, however, she/he has a "claim" (for lack of a better word) that they do not accept returns or exchanges. I've seen other sellers "claim" that they 'are not responsible for items damaged in shipping. How can this be if the packaging was improper, I.e one layer of newspaper on top of all these glass jars? (Not saying this is how my package was packaged, just an example). I have not opened my package yet, I was told to do so at a post office while taking pictures for evidence and a witness. If you do some research USPS insurance does not cover improper packaging from the sellers behalf, I would not get refunded, they would turn me away in a heartbeat.

My question(s) to you:

What would you do in my situation? (i have a feeling the eBay seller is unlikely to compromise, or will want me to return the box with ME paying shipping which was half the price).

Is the eBay seller ( who packaged the item(s) and shipped them, not the USPS) held liable for improper packaging?

Is USPS to responsible for a damaged box? ( it looks like it tumbled down a side of a mountain)

Or any comments or useful information, thank you in advance.

PS: I want my 50 glass jars I paid for, I don't want just a refund.