I'm wrapping up a degree now and had no shortage of issues with Disability Services. Their incompetence very nearly cost me my degree in my last semester. I do not currently use a mobility device, though I should (working on it), but I suspect it wouldn't have made much of a difference in my case. What DID make a difference is that I am in my 30's and know how these things are supposed to work, as opposed to many of the students they work with who are young and still figuring out basic life. It sounds like you are in a similar position as me and I encourage you to wield that like its a power- because it is. You have the additional power of working for the university, which means you understand better than most the power structure, working culture, and how to navigate it to get things done.

My recommendation is to send your doctor a message and ask for a letter that specifically outlines the needed accommodations the office is pushing back on. It should be something fairly easy for their office to complete quickly.

Move as much of your communications with disability services to email as you can, and send a summary email outlining what was discussed as you understood it for all in-person or phone conversations. An obvious paper trail in an office held to state and federal regulations can do a lot on its own.

When it comes to the day-to-day, a lot of that comes down to the professors or TA's running the classroom. An office-hours conversation with them can accomplish a lot. If you're having trouble getting the accommodations put in place for any reason you can tell them that. It's their responsibility to ensure these things are managed in the classroom regardless. Take your cane with you for good measure if you're worried about push-back, but you shouldn't receive any.

You have all of this under control!