I'm agreeing with everyone else - and [rolleyes] at your ex, t3! I guess it can be useful have things put in different ways by different posters, so here goes :) It will be long!
Do abusers know what they are doing? - It varies by individual.
~ Some (many of the abusers on here) have a mental dysfunction that renders them incapable of seeing other people as independent humans like themselves. They view us more like props or tools, which infuriatingly fail to perform as desired.
~ Others, probably the majority, grew up with abuse. It's their expected means of managing a relationship: every interaction, to them, is a contest or battle they must win. They simply don't know any better - and un-learning the basics of one's upbringing is not at all straightforward; most choose not to bother.
~ With some men, it's unconscious male privilege. They fundamentally believe women are inferior and must be kept in their place.
~ Some people genuinely do have anger management problems. They'd rather not explode all the time, and can learn sensible ways of handling frustration if they make the right commitment.
I would think most abusers have some combination of the above issues.
Is it calculated? - Yes, it's intended to achieve a certain outcome.
~ With the majority, the calculation will be an almost instinctive, split-second choice, but it's a calculation all the same (I used to do this.)
~ Sometimes it will be a strategic decision. It may be based on the same kind of "How can I get him/her to do more cleaning?" relationship problem we all discuss at times, but taking for granted that control of the other is a desired objective.
~ Some sociopaths calculate their abuse as a kind of game. It's entirely deliberate, like a cat tormenting its prey.
~ Most sociopaths don't calculate to abuse, as such; they expect people to behave precisely as 'scripted'. Any means of bringing you back on track will be acceptable, pretty much as you might try everything to get your washing machine to work properly.
~ Anger issues are also calculated, though quite illogically. The rager demands to be heard, at any cost to his audience.
Do they know the impact it has? - Yes! To boil it right down, they put their desires in the moment above anyone and anything else. Abuse is intended to have an impact, it's meant to give the abuser a win.
Do abusers ever change? Do they ever want to? - Rarely.
~ Sociopaths can't change completely. They can learn acceptable modes of behaviour, but their conditions render them incapable of relating to other people 'normally'.
~ People who've never learned anger management can learn it.
~ Those of us who grew up with abuse need very difficult, long-term therapy to change.
Most would not be sufficiently motivated to undertake the self-examination involved. Straightforward anger management would be the exception, however it's usually coupled with the need to win: that's a harder principle to change.
Is it abuse if both parties are happy with the dynamic? - Yes, because a healthy relationship dynamic is founded on mutual respect & concern.
~ In your 'traditional' example, there is no abuse until one partner decides to try and control the other's function, by 'making' them clean more, or earn more money, etc.
~ If they cannot negotiate their relationship with genuine respect and concern, but try to force the other's role, they have an abuse problem.
~ If they relate to one another healthily, they will try to work round their issues together and considerately. If there's no workaround, they're incompatible.
People who were brought up in an abusive environment may not realise their relationships are abusive, so blame other factors for their unhappiness (this happened to me.)
Are all men potentially abusers? - No!
~ Sociopathic abusers often try to get their partner locked down as quickly as possible, with the whirlwind passion followed by swift wedding and babies. This is quite intentional.
~ Many abusers have very specific expectations of their relationship, which they haven't fully explained. They get angry when their partner doesn't meet these unspoken requirements.
All abusers have an intense need to dictate the terms of the relationship. This isn't respectful or considerate.
Does the situation put pressure on the man and we all behave less well when under pressure? - We don't all become bullies under pressure. Most people deal with it through considerate negotiation.
~ The pressure that prompts abuse is actually internal, not a response to external factors. Abusers fear losing control of their dominant position.
Would a man be reacting badly as they are scared to lose relationship but are unable to communicate feelings? - No. Even an emotionally illiterate adult can communicate their feelings in a considerate way.
~ Abuse is about retaining control & dominance.
Can any medical reason explain abusive behaviour? - Yes, loads of them! Mental illnesses, brain tumours, diabetes, alzheimer's, loads of other neurological and hormonal disorders, genetic disorders, and chronic pain are all known for causing abusive behaviour.
~ If the condition doesn't respond promptly to treatment, no partner is obliged to put up with abuse because it's not their abuser's 'fault'.
How many relationships out there are completely free from any abuse from either party 24/7 for their duration? - Lots! Though nowhere near enough.
~ This was a lynchpin of my recovery. I had to learn that good relationships are free from abuse, and what healthy relationships look like.
I mean everything on the scale ... no-one is perfect and I'm not sure how realistic it is ... ? - Yes, everything on the scale.
~ Emotionally balanced people get tired, frustrated, reach the end of their tether, and so on. But they don't take it out on others.
~ Emotionally balanced people can say "I'm angry about ..." and they can say it in an angry voice. They do this without frightening anyone, attacking anyone, or breaking anything.
~ Emotionally balanced people can do this with any emotion, negative and positive :)
Wishing you good speed with your recovery, and good support. Be kind & respectful to yourself, first and foremost.