Need help with a discharge upgrade : Veterans

I separated from the Air Force a few years back with a General Discharge. I was court-martialed and pled guilty. I was not discharged punitively, but my unit commander decided to remove me from my shop because my NCOIC was involved in the trial. I was moved into a CSS unit for a few months and told by my shirt that it was up to me if I wanted to stay or accept a discharge and go home. He said it was possible I wouldn’t be allowed to re-enlist, but that I would be allowed to serve out my term honorably. I did not know at the time that I was suffering from PTSD from the events leading up to the court-martial.

When I finally met with my unit commander, he did not offer me a choice, he simply told me that he was giving me a General-Under Honorable Conditions discharge. I did not argue and I went home.

When I received my DD-214 I noticed it said that the reason for my discharge was “Misconduct – Serious Offense” which is strange to me, since that is not the reason I was discharged. Additionally, I am now diagnosed with PTSD by the VA from the events predating my discharge.

According to VA.gov, “Because your discharge was related to PTSD, the DoD will apply ‘liberal consideration’ to your case.”

I am of the belief that I was discharged due to the symptoms of my PTSD, and not for the reason listed on my DD-214. I want to apply for an upgrade, but I was hoping for advice from you all as to what I should do to strengthen my case. Would it help to get a letter from my shirt (who has since separated) admitting that my commander was considering allowing me to continue serving? Also, I have since completed my degree and have been successful in my career. Would any of that help sway the board’s decision that I deserve an upgraded discharge? Any advice would be much appreciated. Thank you!