More than half of couples impacted by ADHD struggle in their relationships. Many of these couples, like my husband and I, have struggled for many years with a slow descent into chronic frustration and anger as 'the ADHD Effect' took over. (To clear the record, we USED to struggle. We don't any more.!)
So I get this quesiton with regularity - when do you know to call it quits? I do think you know in your heart when you just don't feel all the effort or pain or frustration is worth it any more. You feel you've exhausted all possible paths on your own side, and/or you are convinced that your partner simply won't do anything more...and after all that work you still don't like the situation you are in well enough to wish to stay.
But I remember when there were days my heart was screaming 'LEAVE!!!' and yet, I couldn't. How DO you make this decision?
Ultimately, the relationship needs to either bring you happiness (or have a realistic potential to do so) or at least bring satisfaction on some important dimension. There are a number of dimensions I see people consider in this process: keeping the family together is one for some people; financial stability; fun to be with; romantic, dependable, etc. Which dimensions are important to you is very personal. So I would suggest you look at your own value system and ask yourself "at this point in my life, is this what I want?" Think about it realistically and against 'own' your values. So, for example, many adults (men and women) choose to stay in a somewhat sub-optimal relationship until the kids are grown because they value having the family together and, perhaps, wish to see if they get along better (or worse) once the stress of having kids at home is lessened. Others place more value on financial security or fun or love or...There are no 'good' or 'bad' dimensions - the point is only to evaluate your own situation against your own values.
My own story is one of feeling, even in really awful times, that there was a strong core to our love that just happened to be currently covered in a lot of (you know what) but which was salvageable. There were some points at which it was clear that I could be a much better partner than I had been, and so we both felt it made sense to stay at least until I got my own act straightened out. There were other times when it was my husband who needed to clean up his own act and I was the one waiting. Again, we both felt it was worth waiting to see if we could recover and actually discussed it. When one partner is egregiously outside the boundaries of the relationship (for example, having an affair) it makes sense to put a deadline on your willingness to wait it out so that you don't find yourself sliding into long-term misery. If things haven't improved by your deadline, then that's a good indicator it's time to leave. (Note on this: make sure to put a reasonable deadline...then hold to it. It might take a year to clear up and end an affair and frequently takes at least that long to get traction on managing ADHD symptoms after the ADHD partner has genuinely engaged with the project, which is often not simultaneous with the diagnosis.)
It helps greatly that my husband did get his primary ADHD symptoms under control. If he had not, the 'do I leave?' equation would have been different for me because his continued spurts of anger would have been in direct conflict with some of my own closely held values around respect. At some point, uncovering that core of love would have seemed impossible.
There are also logistical issues that may determine whether or not you end a relationship and these must be weighed against how bad things are. Physical abuse is a 'no tolerance' issue for me (and I hope for you) - if it happens, you leave. Get the help of an abuse hotline or your doctor if you fear for your safety. In addition, finances, your physical or mental health situation, and more can make an impact on your decision and that's okay. Nobody else gets to tell you why you should or shouldn't stay in your relationship - if they did I wouldn't be in mine anymore and look at all the fun I would be missing! No, this is your decision, and your decision alone. Understand your values, make your decision pro or con, and stand up for it.