Thank you for using JustAnswer.
I'm sorry to hear about your situation. Is it possible? Yes. Is it probable? No. A settlement agreement reached in the ENE conference (or any settlement agreement in the litigation process) is a contract. You agree to settle your claims in exchange for something in return (usually some form of monetary compensation, but doesn't have to be). That's a contract. There's no law that says that you have a specific period of time to rescind your acceptance of the contract, which means that (unless a contractual defense applies to declare it null and void) the contract is going to be enforceable the second you sign it.
There are quite a few possibilities for a defense to a breach of contract
claim (which would essentially be needed to declare the contract itself null in a "declaratory judgment"). These can be found here: http://www.nolo.com/legal-encyclopedia/defenses-breach-of-contract-claim-33338.html
Note that only addressing "half of your claims" or even more generally making a mistake is not going to be a defense, unless you could show that BOTH parties made a material mistake upon which the contract is based. If the contract fully waives any and all claims, even if you didn't address them, then the court will usually enforce it as signed. A "unilateral" mistake is not a defense, I'm sorry to say.
So if none of the defenses in the link above apply, I'm really sorry to say that the agreement will be enforceable and not able to be rescinded.
I know this is probably not what you wanted to hear, but it is the law. I hope that clears things up anyway. If you have any other questions, please let me know. If not, and you have not yet, please rate my answer AND press the "submit" button, if applicable. Please note that I don't get any credit for my answer unless and until you rate it a 3, 4, 5 (good or better). Thank you, ***** ***** luck to you!