"Could you enlighten me what you mean by that I am not entitled to 50% of my husband's property? Firstly it's not his property but is jointly owned. "
All praise be to Allah.
Islam enjoins that we deal with justice in all of our affairs. For example, if one's husband hits her without right, she is entitled to Qisaas, that is retaliation for what he did, or financial compensation if the wife accepts that. It is stated in Saheeh Bukhari that some of the Sahabah judged for Qisaas even in cases of scratching.
You should keep documentation of any harm that you incurred, and present that to the qualified Imam, and ask that you be compensated for it. Islam is absolutely just in all affairs.
However, there is no such thing as joint property in Islam. This is a term used by the West, since men usually gain control over their wives property after marriage, or vice verse. This is not so in Islam. The husband's and the wife's property remain independent. Marriage and divorce have no bearing on property rights, it is simply the beginning or end of the marriage contract.
If you and your husband contributed to a joint account, than you have to determine how much is yours, and how much is your husbands. In the end, if you pursue this in court, you should be sure not to take more than what is yours.
People will be held accountable for taking others property on the Day of Judgment. A man who usurped a sheep will be resurrected with a bleating sheep tied around his neck, and he will have to carry it around his neck on the Day of Judgment. One should fear Allah and not take another's property unjustly, and that is what was meant.
"My mahr still remains unpaid till this date."
That means you are entitled to it. Add it to the list of what your husband owes you.
"Maintenance during iddah? What about throughout nikkah? Is it not obligatory upon a husband to provide for his wife and children through this time?"
If he did not provide this, and you had to pay it out of your pocket, then it is considered like a loan that you gave to your husband , according to the scholars. Make a note of whatever you paid, and add it to the list of what your husband owes you.
"Mut'ah if he can't provide maintenace do you think he would give a gift after divorce to me?"
This is not for you or your husband to decide, it is for a qualified Imam acting as a judge between you.
"At present I am not in my iddah period as he is now refusing to give me an Islamic divorce."
As I mentioned, you are entitled to a divorce by a qualified Imam, called Talaq-lid-daraar (Divorce because of harm), if everything is as you have stated. You have no need of speaking to your husband about this. A qualified Imam who is authorized to marry, can also give you something in writing stating that he has divorced you by the Laws of Allah, based on the evidence shown to him, if that is what is right in this case.
Alternatively, if your husband signs the divorce papers, then most of the scholars say it is like a written divorce and the same as saying: "I divorce you." and this will count, Islamically. Your 'Iddah will begin from the day the Imam or your husband signs the papers.
"You say something along the lines of if someone hurts us we shouldn't hurt them back as that is not what our prophet taught us, Is beating a woman, a wife considered right in Islam then? "
Allah will judge between all on the Day of Judgment. We should not answer one wrong with another wrong. There is the hell-fire, for the wrongdoers. We need to decrease the overall number of wrongs, not perpetuate them.
In the end, make sure you only take what belongs to you, after having it approved by a qualified Islamic scholar or Imam. Non-Muslim courts do not judge by the Law of Allah, and their rulings are not valid in religious affairs. A man and a woman may get married in a non-Muslim court, but it would still be considered Zina in the sight of Allah.
And in this way, you will be free of any blame on the Day of Judgment.
And to Allah belongs the heavens and the earth.
And Allah knows best.