Stolen iPad without Find My, should I remove it from my Devices?

My iPad was stolen, I had to wait a week to recover my account & found out I can't put my iPad on Lost mode without Find my iPad on. I can't remember if I had turned it on or if the thief just turned it off (they shouldn't have access to my pin code so this seems unlikely). Now I cannot remove the stolen iPad from my Trusted devices list without removing it from all of my Devices, meaning I'll just help the thief clear out the iPad for reselling/setting up their own Apple ID on it.

I am still unsure of what to do. Now that the stolen iPad remains a trusted device, they will get a verification pop-up every time I log on to my Apple ID. I don't think they've managed to unlock it but is it possible they still could? My choice is to either remove it from my Devices and clear the iPad of all my data or keep it as a trusted device with it logged on to my Apple ID...