In this situation you really need an attorney. You need to make sure you do not sign the final decree of divorce and then go to the final divorce hearing and try to explain why you signed the rule 11 agreement and make your concerns known to the Judge. If the judge still rules against you, you can try and see how things go, get yourself back up on your feet, and then file to modify your custody orders on a later date.
Typically, a Rule 11 agreement based on consent can be revoked so long as it is not signed by a Judge. It's a complicated issue, so you probably need to hire an attorney if you don't have one.
You didn't say whether you are represented by an attorney who was part of the pressure to sign the agreement. If so, you should consult them or alternatively find an attorney you do trust. I am a little suspect as to why everyone surrounding you (attorneys, family, etc) would be suggesting one thing that isn't in the child's best interest. You need to seek legal advice from somebody who can tell you honestly what costs and likelihood of success you are up against.
Good luck and God bless!
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