Despondent about degree and feeling like a failure and a disgrace... please help?

You are not too old to start a fresh degree in a course you actually want to do. In fact, I strongly encourage you to do so, because it's not really a career issue for you - it's more a matter of self: self respect, personal pride. It's for *you* that you'll get this degree. And you will not be the oldest person at your university. Don't worry about the age issue. Many of my students are older than you are, by a considerable number of years.