These abusers are real pieces of shit. I agree they should be outed for the abuse, but would caution you to not CTB just because of them. If you are suffering in other ways like me, I get it entirely. That said, I've always thought that others actions are never, in and of themselves, reasons to CTB. You would feel vindicated, but you'll be dead so it doesn't matter in the grand scheme.
As an ex cop, I would caution on delayed emails, as they will likely seize your computer as part of the suicide investigation and all future emails in draft would be kept from sending. Youtube and twitter are good options because the delayed message resides on their servers. If you have a trusted friend, they could hold a handwritten note as well as recorded clips of the abuser's comments to anonymously provide to the police after your death. They did just recently uphold a conviction in the USA for the piece of shit girlfriend of a suicidal teen for encouraging him over text to do it, so the abusers might have to face justice for what they have done.
I get your pain, but suggest you think hard on whether this is being done to hurt them or being done because they are one of many problems in your like. If it is just for them, fuck them, they're not worth you ending your life. Hugs to you Shadowface, no matter which path you take. You have supporters here.