I hope the OP is still reading this thread. I read it last night in bed and desperately wanted to respond but had forgotten my password to log in.
I was in the same situation as you 10 yrs ago. I fell deeply in love with a quietly-spoken, mild-mannered gentlemanly type who had an excellent upbringing and education, and who held a senior and highly respected position at work. He opened doors for me, brought flowers, was always polite and kind, thoughtful and respectful.
Two years into this lovely relationship, we were on holiday abroad. We were in the small supermarket attached to our block of apartments. We'd intended on salad so had put mayo in the basket. Then later we decided on something else, and I blandly remarked (as you would) that we no longer needed the mayo. To my utter astonishment and horror - he instantly blew up in a red rage, screaming at me in front of all the other shoppers and staff. The gist of it was "Don't you think I realise that we don't now need the mayo?" and he went on screaming "did I think he was an idiot", "who the hell was I to talk down to him", "how dare I belittle him" and suchlike.
Whilst he was shouting his eyes went black and his face went bright red, and he was stomping his feet like a two year old child having a tantrum. He was 52 yrs old! I was utterly shocked, mortified, terrified of him as well as profoundly embarrassed as everyone had stopped shopping and were staring at him. He stormed out and marched to the apartment. I burst into tears and followed him, weeping profusely.
By the time we reached the apartment he was back to normal. He unpacked the food and prepared lunch, saw my red eyes and asked me what was wrong. I described his behaviour, and he had no recollection of the tantrum.
When we got back to the UK I posted what happened onto a website that dealt with problems. (I think it was called something like problem.co.uk.) Within minutes a woman told me that she knew exactly what he had, and it was called NPD. He was a "covert narcissist". I'd never heard of either term
I spent the entire day online, my mouth open in astonishment as websites and videos described his outburst exactly -- right down to the black eyes, the red face, and the lack of memory of the tantrum.
When I read your OP about your DP's tantrum I realised that he almost certainly has the same mental condiiton. Sad to report, it's incurable.
I stayed with my boyfriend for another six years. In that time he had only 3 or 4 more episodes of a "narc tantrum" and each time had no recollection of what he'd screamed at me, or of throwing a physical tantrum.
This isn't to say you should stay with him, but to help you understand the mental condition he is probably suffering from.
I suggest you google
covert narcissist
narcissistic rage
red mist rage
etc
and see if the descriptions match the way he behaves. I think they do.
This page is a good place to start:
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“Narcissistic rage” is a term coined by Heinz Kohut in his book The Analysis of the Self when it was published in 1972. It occurs when the narcissist perceives he is being personally “attacked” by someone else.
Grandiose self-worth, vanity, and entitlement are basic characteristics of this disorder; when these are challenged it often leads to narcissistic rage.
Narcissistic rage is a reaction to” narcissistic injury”- a perceived threat to their self-worth or self-esteem. Their rages can be of two types: explosive or passive-aggressive. The explosive rages are just as they sound- explosive, volatile outbursts which may be verbal, physical or both.
The passive-aggressive rages are exhibited as a withdrawal into a sulky, silent treatment as the means to punish the offender."
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Narcissistic Rage Cycle: The 7 Stages of Anger
Rage is a primitive, immature child-like expression of thwarted needs and/or (actual or perceived) invalidation. For most people, anger goes through several levels of emotion, each level requiring a certain level of self-control. According to psychiatrist Adam Blatner, there are seven levels of anger:
Stress Feeling angry subconsciously but not demonstrating it.
Anxiety Anger shown through subtle clues.
Agitation Displeasure is shown without blame.
Irritation A little more displeasure to elicit a response.
Frustration Anger with a scowl or harsh words.
Anger Anger with loudness of speech and expression.
Rage Losing temper and getting into a rage; aggression.
What Goes Wrong?
It appears that narcissists do not go through the 7 stages like other people do. The smallest infraction will send them right to level 7-rage. Why is that?
Their rage seems to be caused by any threat to their ego, and the ensuing rage acts to erase that threat and maintain their self-image and feelings of superiority.
To narcissists, rage is a perfectly appropriate response when they experience any threat to their view of self.
thenarcissisticlife.com/what-is-narcissistic-rage/
also
www.facebook.com/Shrink4Men/posts/10156276196958982?comment_id=10156276303298982&reply_comment_id=10156277745183982
psychcentral.com/pro/exhausted-woman/2017/01/five-ways-a-narcissist-comes-unglued#2
www.choosingtherapy.com/narcissistic-rage/
narcissistfamilyfiles.com/2017/03/04/understanding-narcissistic-rage-and-why-it-is-not-your-fault/