Help with autistic partner

Hi everyone, I am mainly writing to see if anyone out there has any pointers. I’ve read a few posts on here and it has really helped me to understand my partner so thought I would give it a go and post something!

I am NT and my boyfriend of 10 years was diagnosed about three years ago. His behaviour has changed a lot since then, which I believe is because he was masking a lot before his diagnosis. I’m so happy he doesn’t feel he needs to do this so much anymore and he seems in general much happier in himself since the diagnosis. 

However it is still often very difficult to be with him sometimes. I love him so much and try really hard to try to understand the way he thinks and experiences things. He has severe anger and negativity issues. Often shouts and throws things if something doesn’t go his way or is difficult. Like just now, our friends cancelled a meeting we were going to have and he freaked out, shouting at me for being too chill about it, and has been in a terrible mood since. I know he hates change and in particular last minute changes but it’s often unavoidable. Does anyone have advice on how to help him to manage this? Maybe some tips on how I can suggest that needs to find a way to deal with his negativity? I absolutely don’t want him to think I’m not on his side, but we both love our friends and I don’t want to lose them because he treats them badly.  

I also find it hard to talk to him about autism as he seems to shut down or talk to me as if I don’t understand. Almost as if i’m on the enemy’s team, despite me trying to be open and learn as much as I can. Is this something anyone else has experienced and how can I show him i’m always on his side? I feel like he doesn’t want me to be involved in this part of him

Sorry for the long ramble, I just feel quite alone and struggle to cope with the negativity and having to look after him sometimes.