I wonder about the possibility of multi-modal commuting Mike, you live quite far from where you work - would it be possible to ride a couple of miles to a station, train it, then ride the final leg to where you teach?
Also, as per your comment on another thread - consider the option of turning to internal combustion. You can ride a motorbike, and a nice 600 like the Suzuki GSX-650F fitted with hard luggage could really help you out. It is fully faired, friendly and good fun too. You wouldn't need to use it for every journey, but it would certainly help relieve the strain on your body if you used it on alternating days for example.
From what you have said in this thread, it seems like your body is saying that it just isn't able to meet the demands your are placing on it. In the short term this is more unpleasent than anything, but if you push yourself this hard over time, you could really end up doing yourself some harm - which could hamper your cycling when you get older.
It is never nice to be reminded of your body's frailty, but one must listen to the messeges you are recieving, and react accordingly. You know better than most what you are capable of when trained and fully fit, and it is so frustrating to be suffering as you are, but you need a break - overtraining is counterproductive.
Keep us updated as to how you are doing. Here's rooting for you.