I can save you a lot of trouble, actually. You don't need all of this!
Just make a custom 404 page that returns 13 MBs of junk along with status code 200 and has a few dead links (404, so it just goes to itself)
There are no bots on the domain I do this on anymore. From swarming to zero in under a week.
You don't need tar pits or heuristics or anything else fancy. Just make your website so expensive to crawl that it's not worth it so they filter themselves.