I'm new here but I don't think there's anything for you to apologize about. The feelings of helplessness and anger seem to be common and I am afraid I don't have much to offer you except empathy and support - but they're there if you need them. I finished my MBA about a year ago and can't imagine working f/t and going to school so my hat is off to you.
I was in a car accident 8 months ago (wow - can't believe it's been that long - or that it has ONLY been that long) and hit my head on the driver's side head rest. Didn't lose consciousness but I began to notice I has having problems concentrating, focusing, multi-tasking several weeks afterwards. I'm seeing a neurologist and have a follow up tomorrow.
I wish you all the best in your recovery and progress.
CG