XF 1.5 Is there a way to batch delete users and ALL of their content?

(Running XF v 1.5.10)

I've got a batch of ~3,400 users that need to be removed from our boards instance. I know that the remove the entirety of someone's content you can go to each user's account and manually delete, which gives the option to clean out their posts as well. As you might imagine doing ~3,400 user's by hand is sort of a nightmare. So, a few questions.

1) Does the single user delete method clean out all their data or is there anything that afterwards would need to be manually removed?
2) Is there a method for batch deleting a set of user's based on a specific set of criteria like email address, or user ID and does that method clean out all their other data?
3) If there is a method for batch deleting user's that leaves out some user data then A) what is that method and B) what data isn't destroyed?
4) Finally if there's not a good answer as far as best practices to clear stuff out, has anyone successfully handled this problem with either a hack or a kludge?

Thanks for your input.
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