James, first, sorry to hear you're still healing and I hope for a speedy recovery for you.
As to what you're asking for, let me point out the major rubs that you'll encounter.
Ethernet/USB connectivity: Any network connectivity with a modern tablet device is going to be WiFi only, and though a few tablets will have storage connectivity possible through the micro USB port using adapters, don't take it as a given. Any keyboards will likely have to be bluetooth based as well. They really want you to go wireless on this stuff.
The screen size you're aiming for is going to be pretty exotic as well, and any tablet without physical buttons on the sides is pretty well going to be gesture powered.
That said, if you're willing to make the concessions necessary to go wireless and with the screen size, any stock Android device should theoretically work, from the bog standard
Google Nexus 10 to the more exotic
Onyx Boox M92 tablet with monochrome eInk display. There's plenty of PDF readers for the platform. Either way, be prepared to dump around $400 for it going this route as the resale market's considerably thinner for the monsters than the cheaper, smaller tablets.
All things considered and given what you're aiming for, though? Given what I know of your computing and tool habits layered with these desires... I think I know the perfect solution. It sounds like what you really need would be an older Lenovo Thinkpad X61 tablet. Cheaper than a modern Android tablet, gives you the inputs and cable connections you want, lets you keep running Linux, and switches you to a Wacom stylus for screen input. Not the lightest or most portable, but you don't seem to be gunning for that in the first place. Seems like the most logical solution to what you're wanting.
Maybe poke around Ebay or the marketplace over at the thinkpads.com community.