Advise needed, please be kind. I’m in “at will” employment & at risk of being fired/let go since I had to go on short term disability. Want to prepare myself mentally, so I can mitigate the blowback. More details below:

Please be kind as I'm recovering and trying to navigate – while prepping myself the best I can.

I'm in an at will employment status and recently has to be on leave. My employer has shown questionable behaviors and dishonorable ethics when it comes down to treating their employees. My performance has been positive and recognized but I've been vocal about the lack of support in my project and while voicing this concern, seen as “the problem” by my employer. They've placed me in a situation that is isolating and I've been neglected and overworked. It is possible that my boss may let me go or fire me for “any reason” when I come back to work.

Here are my questions:

1. Can I say “I quit” while he is trying to fire/let me go? So that it looks better in my employment record? I worry about how this will affect future job search (not sure if the record will be visible)
2. Is there any difference in terms of receiving unemployment if I just let them fire me instead of quitting?

Thank you to everyone that care to read and appreciate advice you can give me