Being asked to voluntarily resign? Are they just trying to avoid paying me severance and bonus?

So I had my corporate job (in the USA) for about 9 months, and then my family decided to relocate interstate, so I told my company that I could either resign or work remotely. They chose to keep me on remotely, given a trial. Here's where things get ambiguous.

The only documentation I have for the remote agreement is the email exchange with my manager that states:

"Over the first few months in this arrangement, we'll need to assess on an on-going basis whether your role can be done satisfactorily remotely. If at any time and for any reason, I determine that it can't be done remotely, this arrangement will end. You can either voluntarily resign or you can return to work in the office."

I agreed to that.

Now it's been 8 months since I've been remote, my role has expanded, half my team left 6 months ago and I've got all their work on my plate. We haven't even discussed remote working arrangements since like end of April/May (2 months into the arrangement).

My manager calls and tells me that since the team has all left, they're going to build the team up again and change how the team functions, and therefore they don't want a remote worker anymore, and that I should voluntarily resign at the end of the year. This would mean getting no severance, and not getting a bonus (because bonuses are paid out in March).

I don't want to voluntarily resign, because I don't think I should have to. My commitment to resign was during the trial period, and that's long over. And I don't think I have any motivation to resign.

I also told them I would move back, and they said that they want to reevaluate role responsibilities and level and stuff.

Any insight? Should I resign and take the hit? Should I tell him that I refuse to resign and they should do whatever they see fit? What do I do? (Note, I don't actually want this job, I've been thinking of quitting for months... So being let go right now is great, I just want what I'm owed. I was planning on sticking it out till bonus in March.)

Tldr: my job wants me to resign, but I think they're just trying to get out of paying me severance and bonus?

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