The standard is to show that the marriage was entered into in good faith. If the CR spouse can show that, he can get the conditions removed, even if the marriage has fallen apart since then. If the sponsor does not agree to file the I-751 jointly with the CR spouse (and refuses to pay the fee), the CR spouse can still get the conditions removed by filing a waiver (and paying the fee himself), going to the interview alone, and proving good faith marriage. The officer will look at the marriage harder in this case, but if the CR spouse can prove the good faith marriage, it won't stop him from getting the conditions removed.
The information offered is general in nature and not meant to be relied upon as legal advice. No client-attorney relationship is created through this information. Please consult an attorney prior to making legal decisions.
If the marriage is falling apart, then as mentioned, you can file for a waiver of the joint filing to remove conditions. You will need as much proof as possible to show that you entered the marriage in good faith. You will have to pay the filing fee. In some cases, you can obtain a one year extension on your green card. However, USCIS will need evidence to show why you are seeking a waiver of the joint filing requirement prior to approving the application (e.g. a divorce judgment).
You should retain an experienced immigration lawyer to review all the facts, advise you, and handle the case. You can find one through http://www.ailalawyer.com.
J Charles Ferrari Eng & Nishimura 213.622.2255 The statement above is general in nature and does not constitute legal advice, as not all the facts are known. You should retain an attorney to review all the facts specific to your case in order to receive advise specific to your case. The statement above does not create an attorney/client relationship. Answers on Avvo can only be general ones, as specific answers would require knowledge of all the facts. As such, they may or may not apply to the question.