From what you told us you have recognised that your daughter could have ASD, ADHD or some other condition. Meanwhile your husband does not want to get her an assessment and tells you that their is no such thing as asd, ADHD ect.
Your life is difficult enough with trying to get an assessment for your daughter and as she has gotten older you can see more markers towards ASD etc. She has been moved into a specialist school and with an assessment she can get the support she needs to reach her full potential long term.
I would bring your husbands parents and close friends over to your house and have your daughter minded elsewhere.
In front of these people I would tell your husband I have bought these people here to let them know about X (daughters name) and the problems she has. Tell them my husband keeps telling me that their is no such thing as asd, ADHD ect and is refusing to acknowledge that our daughter needs an assessment and help.
Can you tell my husband to stop being an idiot because I had enough of his current behaviour and the stress he is causing me.
I then give your husband a good slap across the face and tell him it about time he realised that your mad with his current behaviour. Let his family and friends see how upset you are
Tell him he either lets your daughter get an assessment and starts to support you and your daughter or other wise he will arrive home to find the locks changed and he can move in with someone here.
Your husband is being an idiot and he needs people to tell him to cop on.
It not easy to acknowledge that their is something wrong with your child. You husband thinks if he ignores this it will go away but in reality your daughter life will get harder as she gets older.
I know that Keith Duffy who's with boyzone has a daughter called Mia. Mia was diagnosed as having ASD. She is now in her early 20s, has a degree and a job. If you Google his name and then hers you see more information about her.
The autism society in the UK, As I am (Irish autism group) have good websites.
Your doing the right thing for your daughter and your husband needs to realise this.