I have a partner on the spectrum, High functioning and I love him more than anything but we struggle and he gets very angry and frustrated and I run away because he can be quite scary. I'm not sure how to cope with it

It might help if you understood how this happens. Many autistic people do not have a reliable ability to recognise their own mood and emotions, it is called alexithymia. When a neurotypical person feels frustrated or wound up, they recognise that this is how they feel, and can do something about it, but autistic people often do not. Emotions for autistics can be a bit like a pressure cooker without a safety valve, and eventually some small incident causes an explosion. This is because they have little ability to diffuse their feelings before an explosion, because they are not really aware of them.