Ok, last reply on this topic. It's not 100% solved, but it's better.
See above for how to upgrade the firmware for the IS5031/IS5030. That's easy and solved.
The speed issues are a separate problem: I will create a second post about them, so ignore all of that here.
The license problems are trickier. If you have the license(s) written on the bottom of the pull out tab, you're golden. If you don't, technical support can't help you, though. I tried contacting sales, but Mellanox's official policy (despite my begging) is to not support EoL hardware. Apparently generating the licenses for both the 36 port enable and the FabricIT (which allows you to use the subnet manager) from the serial number is a pain. They won't sell them to you, and have no plans for making them available. If you do manage to get one somehow, the FabricIT user guide shows how to install them, and that's very easy to do. Thus, I STRONGLY SUGGEST YOU ONLY BUY THE SWITCHES THAT HAVE THE LICENSES INSTALLED ALREADY. Ask the seller, make very sure that they come with both the 36 port enable license and the FabricIT (internal subnet manger) licenses. Offer to send them the console cable and instructions on how to check, whatever it takes. And when you get your switch, do NOT perform a hardware reset. First, go into console-> config mode, and type "show licenses" and write down the license keys (I think they're displayed there in full...you should be able to find them somewhere in there). They are long strings of letters/numbers and dashes. Then you can perform a hardware reset if you need to.
Hope all of this helps someone in the future...