Re chargebacks, post with postage that you can prove it was posted to the address on record with paypal to get seller protection.

As for the other WHY would you even list items that you do not have?

If you are drop shipping then that is the risk you take.

The estimated times for delivery is way out to what shows in ebays estimates.

Without seeing the listings and feedback it is hard to give a more accurate reply BUT it is known that buyers do not read all the terms etc in a listing and more so when it reads like a novel.