Working out where autism stops and anger issues start

My 35 year old partner and I have been together for coming up to 5 years now. Though my partner has not had an official diagnosis of Autism, he is both open and actually accepting that he has Autism (he seems happy to understand his certain behaviours since childhood etc) His behaviours, seem over the past 18 months, I have noticed, are becoming increasingly verbally aggressive. Things that just warrabt a discussion, he gets very defensive, very quickly. Arguments that are very much small things somehow errupt into chaotic episodes, which I find deeply upsetting. He will scream and shout and I find myself doing the same thing back at him, which I'm not used to, nor liking. It's a poor habit we have developed, I know I should be walking away but it's the things he says are so exaggerated, untrue or nasty that I find myself going into self preservation mode and verbally defending myself back.

Within 5 mins of a huge argument, he's asking me if I want a drink or what we are having for tea. He feels me wanting time away from him is me carrying on the argument, which is not true, Im just so upset by the whole experience and need space. He will ask for hugs which I give because he looks so desperate and he'll ask for reassurance of our relationship too- always after an argument. 

He is a very vulnerable person who is taken advantage of by many people both in his past and in his present and it upsets him a great deal as those who should not of hurt him (family, ex partners, close friends) have betrayed him on huge scales. He struggles reading people (sincerity, intentions etc) and the people who gravitate towards him are no good, they just want money and to drag him down. As I am very good at reading people, I try to guide him into people who are genuine and positive experiences for himself. In arguments he'll say Im trying to control him and tell him what to do (again, not the case), he has a teenage child who I do alot for but again, in arguments, he'll say hurtful comments regarding how he feels I dont accept her.

Once the arguments are "over" he'll apologise and say he didnt mean it etc but for me, Im emotionally exhausted now and these words stick, I do everything for him to take away daily stressors ((cook, clean after getting in from work, (we both work very intense jobs) etc)) but I'm no better thought of, unfact, I feel it's having a worsening effect and making me feel Im being taken advantage of.

He gets angry when I cry, he lacks all empathy towards anything in my life and I feel Im just there for his cuddles and reassurance that he relies on quite heavily. He finds happiness in music which I am fully supportive of, he plays an instrument very well and this is his latest fixation (every year or so his has a different thing he fixates on, intently, then switches) We just do not seem to be getting along at all and I worry I am going to start building resentment towards him.

In all things fair, my partner has a huge heart, is a good person with good intentions, but he seems to want to help everyone else but me and Im the only one in this world who supports him but he cannot see it, or if he can, I never feel it. 

So my question is this. Whilst I know there are many traits congruent with Autism, where does Autism stop and start when it comes to moody behaviour for no reason, getting over major arguments after 5 mins and a total disregard to my feelings, in every capacity. All my friends say he is a lunatic with anger issues and it's not autism. Any feedback would be welcome.