The advice you got from the lawyer was poor. The problem with a marital settlement agreement in your situation is that marital settlement agreements become void in Florida once the divorce is dismissed and the couple goes back to living as husband and wife. Your situation requires a post-nuptial agreement. However, predetermined agreements regarding timeshare ("custody") cannot be placed in a post-nuptial agreement and child support must always be calculated according to the Florida Child Support Guidelines system in effect at the time of the divorce, meaning you can't legally put child support in a post-nup, either. You should use a post-nup, but realize that your provisions regarding timeshare and child support will likely be held invalid. Your alimony provision will likely be upheld, though.
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I agree fully with Mr. Rose. You cannot just go and file an agreement without a case. And most of any agreement that you come up with or already have is void. This is much more complicated than you realize and there simply is not a "form" for every legal problem. The advice you got was very poor, indeed.
R. Jason de Groot, Esq., 386-337-8239