Answered I would recommend that you speak with an immigration attorney pertaining to this issue. You may file for divorce; however doing so, may impact the success of your husband obtaining his green card. I would speak with an attorney and balance your options. Best of luck.
Answered Yes, you can file for a divorce. It is highly unlikely that the divorce process would be completed before the U.S. Immigration Service rules on the I-751. However, if impacted, the foreign national can file and obtain the permanent green card under an exception to the joint filing requirement. However,before you do anything, you should contact the USCIS for a status update regarding a decision on the I-751. I recommend that you meet with an immigration lawyer to help you proceed with the best decision for you.
Answered You can but before you make any decisions make sure you speak with an immigration attorney to make sure you are making the best decisions given all of the details of your situation. The process for removing conditions is a bit different if you are divorced from your United States Citizen spouse so it is worth your time to have those differences explained to you. Good Luck.