I see two problems.
1. MST isn't a diagnosis.... The depression and anxiety are. As Broncovet stated, you need to get a Voc - Rehab counselor to specifically say that your anxiety and depression due not allow you to gain substantial gainful employment, due to your service connected anxiety/depression, then state why it hinders you from such.
2. EED - There was no appeal filed, so as you stated the decision is final. Once again if there is something in your service records that the VA did not have available, but should have, then you'll have a chance to get an EED. If the VA had all the documents that are relevant and an appeal wasn't filed you're more than likely not going to get an EED. Seek counsel, there are many lawyers. You could get an EED up to 1 year from the date you filed or intended to file for an increase if you're granted an increase and you have records dating back a year.