I would take a video recording of your screen - Camtasia or some like program. If you start out on your account and video moving around the site and to your page that would be almost impossible to reproduce. Saving a picture or pdf is easy to fake.
I see an issue with archive.org too. First you are relying on a 3rd party for evidence when they could have an issue with the page or lose pictures to make the page unusable or even more likely - the non-tech judge or whoever will be like "Well that's not ebay that's some other site."
A small example of this is: 4 years ago bought a laptop online. It had a buy one laptop get a free mini (worth $400). I felt like the checkout was odd since it didn't mention the mini on a couple of the steps. So I video'ed screen - and a few other sites to get day/time info. 3 weeks later got laptop, surprise no mini. So I email them and they basically tell me to f' off. So I email them the youtube link to video... Within 15 mins of emailing, got confirmation that mini was shipped and an apology and a gift card to take video down.
Video is much more powerful than any other form of medium to handle disputes. Would it work in a million dollar lawsuit... maybe, maybe not. But for anything practical it is more than enough.