[Solved] 8yr old son is really rude and offensive to me

I have an 8 year old son who we think may have some asperges tendencies. He is being assessed at the moment and the doctors have been really supportive. His behaviour at home is often appalling when he doesn't get his own way saying that he wants to kills us, he hates us, essentially saying anything to really try and shock us. He is very physical and uses his strength to dominate his younger sister. He also often hits me. They can't play well together as his games must all be on his terms which means they often fall out resulting in fights between them. After a while things get too much for me and I become really upset resulting in shouting matches. I admit that I have a short temper which on the whole I manage to ignore but when I've had enough, the shouting starts. I struggle to cope with the way he dominates the household due to his behaviour. The home seems a really negative place at times as a result and I don't know what to do. My wife keeps saying that it has to be connected to the potential asperges condition (if he has it it is very mild as even the school are unsure). The dad in me thinks his behaviour is unacceptable and should be dealt with but my wife tries to give him space and exert any feelings he is having as a means to communicate how he is feeling. Being told I'm an idiot, a loser, he hates me etc is wearing me down and I don't know how to handle it. Does anyone have any similar experiences? When he isn't being like this, he constantly tells me he loves me, and I get loads of cuddles. One extreme to the other.