The trick is that when you get booted, do NOT close out your account. Start manually deleting and when you get to the years prior posts and can't go any further because you've hit the archived content wall.. leave the site for a few months or so, keeping your login active.
Just wait.
It's like facebook, in that when you show up after a time it will dig up your most current post to put up on your profile page.. the system is designed to show you your own shit to keep you engaged, so it will unarchive your older content to bring it up. I'm now three years deep into my posting history on old.reddit and I delete a few pages worth every week. When I get to the end of this current batch and can't go any further back.. I'll just wait. I don't even logout.
Patience is the key esp. if you'd been on the site for a super long time (I had 15 years..)
Rinse and repeat until it is all gone.