I have performed Nikah, but not consumated the marriage as we have not done Walima yet. My wife is violatingmy rights. If i leave her, am i obliged to pay mahr, and if so, what portion?

Rasulullah Sallallahu alayhi wa Sallam said: Verily the most detestable halaal act in the sight of Allah Ta'ala is Talaaq (divorce). In view of the above-mentioned Hadith you should avoid giving your wife divorce without having exhausted every avenue of addressing the marital dispute. Almighty Allah says in the Qur'aan "And those women concerning whom you fear disobedience, so advise them, leave them in their beds (do not be intimate) and hit them (lightly)"
In advising your wife, you should be wise and diplomatic as wisdom and diplomacy are the most efficient tools of success. However, if you are unsuccessful in that, then only should you distance yourself from her in the bed, and if that too is unsuccessful, you may hit her lightly in order to jolt her. After having exhausted these avenues prescribed by Allah Ta'ala, if you are still unsuccessful, both parties should appoint their representatives to address the dispute. If the representatives are sincere in their approach, Allah Ta'ala will unite the hearts of the disputing spouses. If you are still unsuccessful, then we advise you make Istikhaarah (Seek Divine guidance) from Allah Ta'ala before proceeding with the divorce. Kindly refer to Istikhaarah on this site. Should you finally decide to divorce her, then if the mahr was stipulated and you were in isolation with her wherein there was no Shari prohibition to be intimate with her, then you have to give her the stipulated mahr. If there was a Shari prohibition, for example she was experiencing menses, then she will be entitled to only half of the stipulated mahr.
The gifts given to her during marriage belongs to her. You cannot claim back those gifts.

And Allah Ta'ala Knows Best.

Mufti E. Desai