I believe all fanfic is made out of thin air, but that's besides the point.
Now, while it's true that my assumption is based more on general knowledge of japanese ghosts and curses rather than just what we are shown in this manga, I was merely presenting a scenario that explain "AxeGuy"'s behavior through motivation (many scenarios can lead to this outcome, so the example itself isn't that important), beyond just saying "it's his task" and calling it a day. After all, "Wheelchair Pusher" is clear that it's taking people to the otherside when they die, and "Famires Goatman" says "Sorry for the wait" or something and all the ghosts in the restaurant line up to meet their fate, meanwhile "AxeGuy" just blindly swings his axe in the hopes of hitting something instead of knowing from the get go, so just my impression here, but the first 2 really seen the have an "assined task" while the 3rd feels self imposed.
Not trying to change your mind btw, we're both making assumptions based on what we want to believe, and it's fairly possible that I end up completely wrong (not that we'll ever know).
That said, regarding Michiru's tentacles, as I said in my previous post, I'm assuming it's now in some sort of dormant/weakened state, due to Michiru's situation having been relieved considerably, hence why it didn't react to "AxeGuy", and as for "Dad's Horse" when it (the tentacles) was still in the "active/aggressive state", my view on the situation is that, the tentacles tried to attack Miko's dad, "Horse" stopped the attack, then the tentacles retracted, not because it "sensed the Horse was okay or the same as itself", but because it concluded that were they to fight, it would lose (as the tentacle was struggling to escape the Horse's grasp, but the Horse was holding it effortlessly), and as such, decided to avoid further conflict since the Horse didn't immediately retaliate. And finally, for the "Big Boss of Old boomer", I can only say: I'm sorry, but it's hard for me to believe that Michiru's tentacles would win against something that tore off 2 tentacles in full attack mode just because "it was distracted with something else and would then focus on the fight"...