I don't see the idea of 8s being cool-headed all time. They are in the anger triad and the type who displays it, while 9s repress it unconsciously it ("forget it") and 1s repress it consciously.
As parallels, the heart types have 2s being the most open with their self-love (as a fix for their love-need). 3s repress it unconsciously, channeling it into need for achievement. 4s repress it consciously and have the battle between elitism and poor self-image.
The head types have 5s being consciously repressive of anxiety (ie. limiting responsibilities, interactions, etc), 6s being most openly anxious, and 7s forgetting their anxiety with the distraction of hedonistic pursuits and novel ideas.
The types which are most open with their center "use" it against others. It becomes a tool almost. 6s use anxiety to protect themselves; that's almost why they look to confirm suspicions or fears. 8s use anger to bully or intimidate others, which gives them power to satiate their needs. 2s use displays or promises of "love" to woo others into giving them what they need.
7s can get bossy or bullying also, as a way to push for their desires to be fed (because the anxiety of having to face any pain/boredom/whatever begins to creep up), but they try to please & coerce more. 8s may just BLOW. IMO, this is most true of se-dom 8s. I'm quite sure I know an ESFP e8 and the dude just has no hold-back. It's not fear-drive, it's just like he's quick to punish or assert power by screaming at someone if some desire of his is being opposed. This is very much anger-driven, and they have no hesitation to unleash it on someone; it's like a toddler screaming for their way - there's an entitlement in their lust. Is there is a threatened theme? Is there a rush towards the fears? Yes. But this is not out of line with 8 traits. Consider these points Naranjo aligns with the low-functioning 8: hostile affectivity (flares readily into arguments & attacks), assertive self-image (proudly characterizes self as self-reliant), malevolent projection (claims others devious, controlling, & punitive; justifies own mistrustful, hostile & vengeful attitude by ascribing it to others).
The trait structure mentions under lust: a pleasure in fighting for pleasure.
Under punitiveness: "Of all characters, this is the most angry and the least intimidated by anger)... This character retaliates angrily at the moment & quickly gets over his irritation".
Under dominance: "Hostility may be said to be in the service of dominance, and dominance, in turn, regarded as an expression of hostility."
Insensitivity: "confrontativeness", "intimidation", "disdain for... weakness... & particularly fear".
Conning & Cynicism: skepticism, distrust the motive of others
Exhibitionism: bragging, arrogant claims [that are] consciously manipulative
Defense Mechanisms: "over-masculine" 8 strives through excessive assertiveness & aggression to avoid "feminine powerlessness". Guilt-denial and unawareness of pain (as a result of conscious absence of shame- sadism & punitiveness towards the self). "explains typical attraction of lusty people towards anxiety, which is not avoided but sadistically transformed into stimulus."
On the surface, cp e6 & e8 may certainly share some traits. What people point out as markers for cp 6 seem to be shared surface traits.
Naranjo's 8 sounds more like Jung's Se-dom (whose Te-dom sounds very much like Naranjo's 1). I don't think either successfully separated the etype fixation from the cognitive preference, but in reading each, it's clear Te-dom seek "restraint" more than Se-dom, so a TJ 8 may be less explosive than a Se-dom 8.
Also, 8s are reactive types, along with 4s & 6s.
I have a feeling many are imagining an NTJ for e8s. NTJ e8 is not going to look like Se-dom e8. S-doms are arguably the most emotionally driven types. ENTJ e8, with inferior Fi, may internalize anger & then unleash it via some strategy. That's not a Se-dom style.
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I have no invested interest in the OP's type (but find e6n witch hunts silly), but the main 6ish element he's described for himself is that for some reason people seem to think he needs protection (or something like that). This is more of how people react to 6s, as even cp 6s can have phobic aspects such as drawing others to you for support by seeming vulnerable. That I don't see in an 8, but nothing else really stood out to be as decidedly non-8.