The best thing to do will be to not divorce ....
When your I-130 & I485 are pending at the service center and you divorce the USCIS doen`t know about the marital status , they processing the case on a regular basis , but if you tell them that you are divorce , they would deny the case and start the deportation procedure . Even if you cannot get along with the spouse , it is always better to find a way to wait till your case is approve and then divorce after . But if it is a real pain , there is always a way to obtain the green card if you can proove that the relationship is a hardtime but i beleive you are suppose to be married at least for two year in order to proove your case . The other option will be if you are divorce to do not tell the USCIS about it and find a way to convince your former husband to just show up at the interview time .....Sometime they already approve the application but they just want to make sure that the person on file is the one that is on front of them.....