Partner Threw Out Meds Causing Anger Issues to Save Relationship

My boyfriend has ADHD and we've been together for two years now.  Throughout that whole time he's had problems with sever anger outbursts which would turn into fights lasting hours and sometimes days.  I won't get into details but I will say his treatment towards me during these fights was mentally/emotionally abusive.  It's like he flicks a switch and suddenly he's a completely different person, screaming at me, spitting, etc. I'm sure a lot of you can relate.  Once I pointed out during a fight that he was abusive, he started to put more effort into dealing with his anger issues.

A few months ago we had the worst fight we've ever had.  I ended up breaking up with him which only lasted a couple days.  I love him with all my heart so breaking things off was the hardest thing I've ever had to do, even if it only lasted a couple days.  After that he put so much effort into controlling his anger.  We went weeks without fighting; It was wonderful.  It felt like we had a normal happy, loving relationship.  Of course it wasn't long before he was tearing a strip off me again, and again a couple days later.  The last fight was on Sunday when I broke up with him for the second time, and once again it only lasted a few days.  When I've told him I want to end it, it's partly out of anger but also out of fear of dealing with the emotional abuse for the rest of my life.  When things are good between us they're REALLY good!  We're perfect for each other, but when things are bad... oh my god they are BAD!!!  

He started taking Dexedrine just before we met and said he never had problems with anger before the medication.  It works wonders in every other way, except for the mood swings/anger issue side affects.  To make matters worse, about 3 months ago he started another medication, not related to ADHD, which he has to stay on for another two months.  This medication also causes mood swings/anger problems.  Out of fear of loosing me, he through out his dexadrine.  Well the last couple days have been an emotional rollercoaster for him (and me of course).  He wasn't able to get out of bed for two days, he's had a couple tantrums (luckily not directed at me this time) and he's struggling to get any work done for the business. 

Has anyone experienced something similar with the medication or noticed your partner going through similar side affects from taking the meds and coming off them?  I don't want his life thrown upside down if he can't function without the meds but I can't go through another fight caused by his medication's side affects; I don't think I'm strong enough anymore.  Any advice, suggestions, or similar stories?