Incidents at school will lead to exclusion

I am so anxious and worried for my 7yr son at the moment. In year 2, my undiagnosed son had a very difficult time at school which lead to so many incidents that included biting and hitting teachers. When he started year 3 in September, he really seemed to have improved, until 2 weeks ago when the school tried to make him more independent he lashed out at his teacher punching her on her chin and pulling her hair. I was called into school and told about the situation. On Friday just gone, the same happened, His support was taken away and he lashed out at his teacher pulling her hair and telling another TA to shut up. I was called into the office after school and was basically told that next time he is out. I am with the school, this is totally not on and he knows not to hurt anyone. The reason I am so sad is because he is such a kind, gentle, caring, intellegent little boy and this only seems to happen when his support is taken away from him. He does not actually have any support for himself it is the class TA who tries to support him as much as possible. I just feel they are taking the wrong measures with him because ''He does not have as many issues as some of the other kids in the school'' (said by the head). I have asked for an emergency meeting with SENCO but I don't have much hope for this week and have that sinking feeling that he will be excluded. I am doing my best to fight for him but it just seems that no one cares (School and authority) I have no family to talk to for advice, my mum just passed and my husband really does not understand ASD and all that is going on. I just wondered if anyone has had the same issues with school and what did they do? We have also been told we are atleast a 10 month wait before diagnosis so can't get outreach support. I requested the school to apply for a EHCP but they have told me they don't have enough evidence :( 

Any advice would be greatly appreciated