Have either of you explored the natural supplement route. I was many testosterone boosting supps while bodybuilding and surprisingly a lot of products work really well. I worked at The Vitamin Shoppe for some years and through my continued experience I can suggest the following:
http://www.lpsg.com/5281474-post6.html - Any ?'s here lemme know plz.
As far as exercise. What you posted is not gonna be enough and the treadmill alone will not do it. Everyman should be lifting weights if he wants healthy erections and overall good health because it really helps. Compound movements are the best:
Squats, Deadlifts, Clean and Press, Walking or Standing Lunges and Squats, Squats and more Squats. Doing these excercises maximizes blood flow and will increase testosterone and growth hormone production.
The next thing I would try would be to take the focus off sex. Don't talk about it for a long while. Just let it go. Even though your understanding..... believe me it's probably killing him inside. He prob feels totally helpless and lost. You should try to pleasure yourself for a while and leave him out of it totally. Maybe take a shower together every now and then and touch him down there just to play and see if you get a reaction but don't make it a thing like "i'm touching you here to try and get you hard for sex right now". And, when he sleeps or right when he wakes up stroke him and see what you get..... again, not a "i'm stroking you cuz I want sex right now" just a "i'm stroking you cuz I still love your cock and I just wanna feel it". Hope that makes sense.
It sounds like your doing a great job as is and are really understanding. He is lucky to have you at his side cuz another might not be so understanding and helpful.
Next, diet.....VERY IMPORTANT.
Hydrate, Hydrate, Hydrate and not just water. Foods that hydrate you should be in abundance....... think plenty fruit. Watermelon is the best as it has high amounts of citrulline which your body converts to arginine.
Cut out the fried foods and as much processed food as possible.
Hope this wasn't too long and is very helpful and the best to both of you!