Just want to add more details so that people in the forum are more comfortable with the idea of contacting congressman/senator. Each congressman / woman / senator has one or more dedicated staff for handling interfaces with federal agencies such as USCIS. Normally, congressman or senator has more than one office location (in my case three offices for my congressional district in NC, "Yay! Gerrymandering"). Most likely only one location will house that staff person. So it may be a good idea to call the office and ask them about assistance regarding a pending application with USCIS. Then find out which office location handles interfaces with USCIS. If the same staff is rotating between offices, then find out the location and time when they are available.
Some congressman offices are advanced in the sense that you can do it online. You need to fill disclosure form along with ID details for them to verify your identity. Then you talk to them over phone. Mostly they will ask you to come to the office.
Once you go there, you wait for your turn and meet the staff person. It is the personal connection that is important. If they realize that you are going through a lot of pain to get a green card, then they are most likely to help you. Don't act too smart. Listen to them and express your grievances to them. The congressman has a dedicated support line with USCIS and gets much better and accurate responses. There was an online presentation from USCIS explaining how this thing works a few years back. Maybe you can Google it.
A big "No No" is asking for help from Congressman and Senator at the same time. They will eventually find out and figure out that you are wasting their time. Also don't incline to show your Political preference. They are doing a job that is paid by the taxpayers. Of course they will be happy to hear that you support the congressman. However, there should not be such pressure normally.
Once you get the positive outcome for your case, please call or email the staff and personally thank them. This is just basic courtesy.
As a byproduct of availing this help from congressman, you will be added to their mailing list. I think I got mails for three years and one day it all stopped. It is just a minor inconvenience.