As it is compromise settlement, the terms in respect of custody and maintenance of the child, you both should come to agreeable terms, and those terms should be only, I repeate only, keeping the welfare of the child and not to satisfy the emotional and ego needs of father and mother. So, whether it will be two visits in a week or an over-night stay with the father shall be decided by both of you, keeping in view of the interest of the child. But as far as re-marriage is concerned, you put it in black and white in the settlement, in the event of her marriage, permanent custody will be with you and she will have visitations rights of a week in the whole year. Similarly, if you would get married, the same condition will apply and she will keep the permanent custody with a week's visitation rights to you in a year. It is only a suggestion. You can modify the suggestion according to the circumstances and attitudes of the parties. By your post, it appears that she and her advocate are reasonable and you can bargain with them. But whatever may be the agreed terms, those shall be reduced in agreement, so that there will be no future complications.
If you both will not reach to any agreement, then you can come to agreement that the matter will be referred to court, whose decision will be final in respect of custody and visitation of the child.
Regarding maintenance amount, first of all, you clear in your mind that out of 15 lakhs, how much you want to give it to your wife (whether that amount is acceptable to her) and how much would be your son's maintenance? If it would be five lakhs for your son, you can put the conditions that this amoount will be put in fixed deposits by breaking the amount of Rs.75,000/- each in the name of the child,, whose maturity period will be with one and half year gap. Suppose, the first F.D. of 75,000/- can be realised only one and half year later, the second
F.D. can be realised only 3 years later, so on...