If you're concerned about your husband's status you should first speak to an immigration lawyer - but if you have a permanent green card you're OK.
Under the rules governing the conduct of attorneys in New York it may be necessary to remind you that this answer could be considered attorney advertising.
If you get divorced before your husband becomes a citizen and he is here illegally he will not be eligible for citizenship. However, a divorce right after he becomes a citizen will look like potential immigration fraud. I believe you need to worry about yourself and your interests which appear to get a divorce now. I highly advise consulting with counsel.
You should consult an attorney. Even though immigration attorneys are expensive, you really need someone who can examine the details of your case, not just general answers on a Q&A forum. Good luck!
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