Hi NeatsZiggy,
I have much empathy, compassion and respect for yourself and your current situation.
Your story is pretty much identical to mine. My partner of three years, is currently going through an extremely rough patch of life, and I am his only 'support network'.
Maybe I should mention that I am a Student Nurse in the final stage of study; which I tend to blame for my extreme interest, compassion and willingness to help in regards to mental illness.
I myself, have 'depression' but any person walking past me in the street wouldn't have a clue. I am past my rough patch, and could possibly say that I am in the best state of my life.
Going back to 'being on the receiving end' - My partner has a history of aggravation as well, he is a very anxious, and agitated person naturally, and he always has been (excluding when he was pursuing me). Throughout our years of being together, I have gained a high knowledge of his 'triggers' and what strategies I can imply to assist him with his panic attacks. His triggers for panic attacks are 'not knowing', such as misplacing something and not being able to find it ie. Keys.
The only way you two are going to get through this as a couple, is if YOU stay strong. By the sounds of it he takes a majority of things out on you, either purposely or not. What you need to understand and keep reassuring yourself of is the fact that he is not under control of his current states, and if he was, it wouldnt have happened.
You also need to understand that whilst he may have just been verbally abusive towards you, his mind is racing trying to figure out why he has become so aggravated, and why he has had to react in such a way etc. I found that if I walked away from an argument (we used to argue uncontrollably), and came back to him 5 minutes later, his frame of mind had completely changed and he was apologetic and absolutely lost as he couldn't understand what had just happened himself - in other words, loss of control.
This is where you understanding and reassurance comes in.
Generally chatting about how he is feeling, even if he is repeating the same thing every day assists them. Encourage him and point out his positive aspects. If you see an improvement one day compared to the day before, make sure you mention it. Tell him you are proud of him. Make him his favorite dinner by surprise, and have his favorite dessert waiting. It's tiny little things that can impact their mood.
When I was down and out, my partner used to grab me by the waist and hand and dance with me in the lounge room. I do the exact same to him now, and I have never seen such a gleaming smile. The main thing your partner needs is a continuous positive energy that is understanding at the same time.
Most importantly, is you taking time out for yourself, even 10 minutes. I'm unsure if you watched the Mindful 10 Minutes video, but if not definitely have a look. I gained a lot from this in regards to mental stability of myself.
I'm currently in the process of making personal short, medium and long term goals with my partner to assist him in the process. Have a look in this? Also a list of activities which help him calm down, relax etc. Sounds silly, but definitely helps!
I hope this little bit of advice / personal experience helps.
Good Luck for all future endeavours! Your will see a change in your partner, just continue to stand by his side.