You can do it!!! Dont question yourself, just do the best you can! Look at that GPA you got! And dont worry about being older than the average aged student. I've had a couple of adults in some of the classes I've taken over the years. My mom just graduated from law school last year, and she just turned 55! I agree that if you're having troubles with your instructor, go to the head of the department. You could always look into the disabilities program on campus, or perhaps they have a program for non-traditional students that you could also get involved in to help counter-act silly professors who dont appreciate learning at any age.
Students like you are an inspirtation; dont worry about what those around you think. Keep your head up!
Best wishes!
Ro