Lowering my own standards to accomodate an ADD-man?

I just found this great site and it seems so helpfull that I decided to share my own experience, to vent, to get a second opinion and yes, maybe some sympathy too. 

Compromising between for example the zoo or the beach is a realistic task.  But is there any compromising between decent and disgusting table manners?

My SO is an ADD man, and I am the non-ADD woman.
In short:  We are both nearing the age of sixty, we both are not working anymore. We both have a university degree. I am European, and English is not my first language. Also he has more of a working class background, while mine is educated middle class.
We got into contact over the internet, and spent several month with an intensive and extensive e-mail and telephone contact, before we met. During this time, he seemed a dream come true, because we seemed to have so much in common, to share so many values and attitudes.
When we actually met, everything changed. 
We are together right now, but if we are not getting married, we have a lot of trouble to be able to be together all the time in one of our two countries. So he wants us to get married, but I have become such a wreck from being the target of his inacceptable behaviours, that I feel I should run. We can stay together for another 5 month, then decision time comes. 

He has no official diagnosis of ADD, he has been misdiagnosed and given anti-psychotic medication for a while, but luckily he is off that by now. One doctor told him, that he has ADD, on a computer test he also was ADD, and he has so many of the typical symptoms, that I have no doubt about it. He denies it, my mentioning ADD causes anger, and he interpretes all my reactions to his behaviours as an indication that there were something wrong with me, not with him. He demands me to change my attitude and to lighten up.

When we met personally, I started to experience on a daily basis unpleasant emotions until I was burned out. That feeling of being burned out has already been discribed in other postings much better than I can do it.
I have gone through it all, pain, frustration, repulsion, humiliation, stress, embarrassment, until by now I have lost all my calm, composure and countenance and I am loosing my temper at every unpleasant incident. 

Apparently, we have different standards of what we consider as appropriate and normal in things, that we never talked of while on the phone.

I need some feedback: Can he really demand or expect me to compromise with his behaviour, which is so far off from what I consider civilized, or do I better acknowledge, that the differences are too big, and there is no future?

In the first weeks of being together, I found out:
He did not change his underwear or T-shirt for days but slept in the same he wore during the day.
He sometimes did not take a shower for days.
He did not use sheets on the bed.
He did not lift the toilet seat while doing his business standing. The seat had gone ugly and needed to be replaced.
He wiped his nose on the sleeve of his robe.
He shoved food upon his fork with the finger on his plate and then moved the unwiped hand down upon his lap.
He used his paper napkin to wipe his placemat and afterwards used the same with his mouth.
He shoved crumbs (and other debris) from the table into his hand and then put it upon his plate, before he had finished eating from it.
He did not wash any fruit or vegetables before cooking or eating.
I use the past tense, but sometimes he still relapses into doing some of those things.

I was shocked, it had been beyond my imagination, that an educated person could have such manners. I told him bluntly, that such behaviour disturbed me. Reluctantly, he tried to improve. But I could not convince him, that he needed higher standards of manners for his own sake, and that he was responsible for this. Instead, he attempted to change his manners just to please me, or even just to avoid my reactions. Such an extrinsic motivation was of course not strong enough for any progress without collateral damage. Instead the spiral of deterioration began.
When for example he wiped his nose on his sleeve the first time, I told him calmly, that I considered this as inappropriate behaviour and I wanted to convince him of this. But on every new occasion, I got more drastic, and after a few repetitions, I was cringing with disgust, and yes, at some times, I called him a pig, because that is my true opinion of such manners. I got frustrated, that no matter, how drastic I was, it did not motivate him to stop. He got angry and aggressive, because I nagged him for what he considered trivialities.
Who has to yield, do I have to allow him the ADD's license, am I obliged to sit at the table and feel repulsed or is it his obligation to spare me the disgust of his manners, or do we better stop sitting at the same table? Personally, I think that sparing the other the feeling of disgust is part of caring.

I am fully aware that pointing out to someone his bad manners is a way of making him feel bad, and my role in a relationhip is also to spare this to him and to make him feel good. But how can someone change his manners, when he has no glimpse of how his behaviour sometimes is embarrassing and disgusting, to me and in public?

This is just the beginning, there has happened so much more, of which I would like so much to know, how much of my consternation and outrage about it is justified. But this post has already gotten very long, so I might continue later.