Which ways can be used to log in to WordPress?

wrote something long and decided to delete because the Tl;Dr is use a good password and stop pretending to have a knowledge in how to secure sites, you are more likely to bring down the performance of the site (your reverse DNS code) or lock yourself out then actually preventing an attack.

Security is about context, and in the context of wordpress brute force attack is probably the least of your worries, it would not have prevented you to be hacked via
http://wptavern.com/wordpress-security-alert-new-zero-day-vulnerability-discovered-in-timthumb-script

or http://wptavern.com/critical-security-vulnerability-found-in-wordpress-slider-revolution-plugin-immediate-update-advised

or https://blog.sucuri.net/2015/10/security-advisory-stored-xss-in-jetpack.html

And before even getting to plugins maybe I should have asked is your hosting secure? (can’t find the link and don’t remember which big hosting company was hacked)