Provided that your letter makes it to your ex-husband's file, he will be called to an interview and very closely questioned about his marriage to you having been a marriage of love entered into in good faith and not for the sole purpose of evading existing immigration laws and procuring himself a green card.
You must also keep in mind, however, that your ex will most likely be invoking one (or more) of the numerous existing exceptions to the joint Form I-751 filing requirements, among which the "good faith" exceptions and allege while he married you for love and was very much in love with you, that you gradually became unstable, etc., etc., and that it came to a point where for his own sanity and well being he couldn't take it anymore and had no choice but to move out and seek a divorce. I bet you, aside from a detailed sworn personal declaration recounting his gradual " descent to hell" he will also obtain a clinical psychologist's report about all the "emotional distress" and "abuse" he suffered as a result of the "highly unstable" and at times "abusive" relationship he'll claim to have had with you. It will end up being your word against his. He might even manage to obtain couple of sworn declarations from some of the common friends or acquaintances you might have had..
Even if immigration ends up denying his I-751, he will have another chance to remove the "condition" in immigration court. There, in front of an immigration judge, his lawyer will undoubtedly argue that the legal burden is on the government (and not his client) to prove that there was marriage fraud in this instance and that the gov. Has thus far "failed" to meet its burden and instead only reached its decision by relying on circumstantial evidence based around the allegations of a "spurned, disgruntled" ex spouse engaged in a "vengeful vendetta" against his/her client.. Based on these arguments and the legal burden which USCIS will likely never be able to meet, the IJ will most likely side with your ex and grant him the permanent GC.
Your only hope is that your ex is stupid and arrogant enough to think he can pull all this by himself, without the need of a competent and experienced immigration lawyer. Am afraid that might not turn out to be the case, however.
The best advice I can give you is to forget and move on with your life, before you get hurt much more (needlessly).
If it is foreign men you like, that's OK, but next time please make sure that they already have at least a green card?
Behar Intl. Counsel 619.234.5962 Kindly be advised that the answer above is only general in nature cannot be construed as legal advice, given that not enough facts are known. It is your responsibility to retain a lawyer to analyze the facts specific to your particular situation in order to give you specific advice. Specific answers will require cognizance of all pertinent facts about your case. Any answers offered on Avvo are of a general nature only, and are not meant to create an attorney-client relationship.
This issue has come up frequently in our practice. There are avenues of redress available to you if you choose to pursue them, such as contacting a fraud hotline and, as the previous attorneys mentioned, sending a letter to USCIS to apprise them of the situation. Once such a letter is received, it will most likely remain in this man's file for the rest of his immigration "career" in the U.S. I would imagine the letter would adversely affect his chances of further progression up the immigration mountain, so to speak, though every case is different.