Use your wisdom before venturing into taking Divorce. Your child will be the most effected.
In reply to your post, if you file for Mutual Consent Divorce (MCD) it may take around six months to one year from taking your case on record by the Court.
However, you need to comply the provisions of MCD in order to convince the court about your issue.
It is your moral responsibility to maintain your spouse and child. If she goes for maintenance you may have to shell out huge sum of money.
Coming to question of Maximum Maintenance, the same depends upon your social status, earnings and also other issues viz., your other financial obligations etc. The court will take all these parameters in to consideration before awarding the same.
However, since you are planning to go for MCD it can be taken care by paying a one time settlement viz., Permanent Alimony at the time of Divorce (all claims, settlements will be covered here), till then you need to take care of your spouse and child.
Think and act before you finalise.