https://ssd.eff.org/en/module/protecting-yourself-social-networks
Also -- have you tried the steps described on Twitter's
"Deactivating your account" page? I know next to nothing about Twitter, but this looks like it should work. I hope that's helpful.
I don't use my real identity online, although I am not a celebrity or even slightly well known -- so I have a luxury that government officials and public figures don't have.
Despite taking precautions, though, it would be all too easy for anyone to be -- for example -- tagged in a Facebook photo and then for their face to be linked to, say, a photo from a protest march, or a pic from a work-related or charity event, etc. And once a malefactor can determine your identity, they can find out all kinds of stuff about you via easily accessed public records. For example, if you're a home owner, your home address is a matter of public record in most places, and it's not hard to determine or at least deduce a lot about your financial status from property tax records, etc.
Even though it's not possible to achieve 100% privacy, I'm as careful about it as I can be, despite the low risk that I could piss off anybody who'd want to come after me (YET!).
The modern world can be a dangerous place, and in this neofascist moment we all have to be a lot more careful than we're accustomed to. At the same time, this moment demands that we take a stand and oppose the new regime where feasible, so it's a balancing act. We all have to think hard about juggling what's best for society and for the personal safety of ourselves and our families.