Re: Should I or should I not?
Don't go into a marriage expecting someone to change. It may happen, but it's not a guarrantee, and marriage is not a way to "fix" people.
Your post makes it seem like you've already made your decision in your heart, you want out of this marriage. If that is the case, and you are sure, then do it asap. It is best not to delay until after the ruksati.
I wish people knew that having an arranged marriage is not the same as marrying strangers. Too many lives have been hurt in this manner. I hope things go well for you.