You have an additional ground for your alimony to stop, and it's a better ground than the "substantial change of circumstances" caused by her remarriage, assuming the type of alimony you pay is permanent. Florida Statute 61.08(c)(8) says permanent alimony MUST terminate upon remarriage of the recipient.
Anyway, no, you do not have a right to request a financial affidavit nor mandatory disclosure from her husband, but you may be able to request discovery, which is slightly different. If you are paying some form of alimony that doesn't terminate on remarrieg, or if you are still trying to make the "substantial change" argument instead of the statute argument (though I don't know why you would do that), you have a good argument that you can take her husband's deposition and request third-party documents from him and get the same documents and information you would get in mandatory disclosure. You should probably get a lawyer to help you. I assume you pay enough alimony that the cost of a lawyer is definitely worthwhile.
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The short answer is "no." Financial affidavits and mandatory disclosure are documents that may be obtained from parties to a proceeding. The new husband is not a party to your post-dissolution action. However, backing up a little, if your Final Judgment of Dissolution provided that alimony was to terminate upon remarriage, then you most likely would not require financial disclosure from your ex, as alimony would terminate regardless. If the terms of your final judgment do not terminate alimony upon remarriage, but still make it modifiable (possible if you entered into a settlement) then the new spouse's income could be relevant for an alimony reduction to the extent that the new spouse's income reducese your ex's expenses. In that case you would have to subpoena this information from the new husband...and expect objections to the subpoena. Good luck!
You cannot obtain financial discovery from her new husband. As far as the alimony goes, it depends on what type of alimony was awarded to your former wife. If the alimony can be terminated due to your former wife remarriage, then you should be able to file a motion to terminate alimony instead of filing a petition to modify. Modification of alimony and termination of alimony are distinct and governed by different laws. I strongly urge you to consult with an attorney and allow him/her to review the final judgment.