As for Headhunter, it is not just that you aim right above edge, you only need to be directly adjacent and aim to the wall and be fully zoomed in to activate monster freezing.
If you fire right away when not fully zoomed in, you sometimes are unable to move for few seconds, like when you hit someone.
This happened in both GZDoom versions r1402 and r1415.
As for Bouncer... Hmm. Instead of increasing the hitbox size of bouncer ball, how about making kick more receptive to bouncer ball? Hopefully I can explain my blabbering...
What I am trying to say, is it possible to code the kick being more bigger just only for bouncer ball? Or is there too much code to do?
As for your "talkthrough," it's was surprisingly entertaining.