1. If it doesn't make you feel too old, a walker will offer better stability.
2. Maybe you need better shoes, to offer better stability if your feet drop.
3. Can you take off a little bit of time from work, and then decide if you want to retire?,
4. Viable other exercise options: swimming, when you don't have a cast. Juggling, with something light- beanbags, maybe. You can try sitting and juggling even with a cast and while I can't guarantee it will lower your blood sugar, it generally has lowered mine (a lot!)
Maybe it's not time to quit but just time to shift gears. I would prefer not quitting but rather making a few adjustments.
Jonah made some good suggestions and I'm sure others will also.
I assume you have considered whether or not you could afford early retirement. If not, find out what programs your state has to offer to help people who find it difficult to keep working or who can no longer work due to health issues. Keep in mind it won't be easy to find a full time position once you quit. You might consider stop singing until you can walk on two feet again. Ask your doctor/physiotherapist what you can do for exercise meanwhile, though even walking with crutches will give you a good daily exercise routine, but only if you are able to do that. You didn't say how bad the neuropathy is, or if it's on both feet, the good leg or bad leg. Also, if you can only see out of one eye it is a concern that you're not seeing properly and it doesn't help when you have trouble with balance. You need to contact an organization that helps the people with various degrees of blindness cope with everyday living. Even you are only blind in one eye that can greatly change how you physically see things and it can be a huge difference between how you see and how a person with both seeing eyes can see. You didn't say if you discussed this with any professional. Don't just quit. Find out how you can improve not only your life but also your outlook on life. Keep me posted on how you're doing.
If you think your problems have anything to do with your vision (lack of depth perception, not seeing things to one side, etc.), there are organizations that offer orientation and mobility services/training. Orientation and mobility is essentially a) learning how to to get from Point A to Point B with little or no vision (if needed), and b) being able to actually get from Point A to Point B safely and efficiently.
O&M instruction can include learning how to use tools such as low vision aids and a white cane (if needed), but instructors also work with people with relatively minor visual impairments on ways of making up for information and environmental cues they may be missing.
Since you live in the States, I believe there each state offers their own services, but if you are at all interested in looking into it, a good starting point is the AFB's Directory of Services. Lots of people wait until their vision is quite impaired to seek out these services, but you don't need to be legally blind to benefit from this type of instruction.
Once you are healed, the walker would probably be a great idea as it gives you that "line of defense" if you miss your step. Short of that, perhaps a cane (or two) might help.
Dumbbells are also good for a sitting or even prone workout.
I am new to this site and have had nothing but good advice and now I think it might be my turn to share some of my own advice. I believe that it is never time to quit or even slow down. I am a marathon runner and just completed the Ottawa half marathon this past Sunday and let me tell you that there were people there much older than me in much better shape. How can they run faster than me when they are double my age? Because they never slowed down! You may need to adjust your activities according to your situation but there is always something that you can do. I heard a motto recently that I try to live by and that is "Sweat at least once a day". It doesn't matter what you choose to do as long as you do something. I believe that you got some good advice from others about different types of activity such as swimming and juggling but ultimately it's up to you to find something that you enjoy.
I know that it's not always easy to live with Diabetes but it is possible!
Good luck and all the power to you!
Another discussion (http://www.tudiabetes.org/forum/topics/neuropathy-complications-wha...) talks about taking R-ALA for neuropathy. Maybe there's some info there that you can use. Keep plugging along!