We learn to balance by losing our balance and then re-gaining it. Perhaps holding onto the fence is keeping you from losing your balance in any significant way. For the short stretches you ride forward, unassisted, maybe you are just relying on the momentum of you and the unicycle to stay upright.
I am not suggesting that you ditch the fence…I used a fence extensively in the first month of learning to ride the unicycle. Specifically, I did a lot of isometric exercises on the unicycle while holding onto the fence, twisting, moving the pedals around, etc. It may be a good idea for you to ease into every practice session with a set of exercises designed to increase your range-of-motion; that way, when you start flailing madly to maintain balance (as beginners tend to do), you won’t injure yourself.
The trick for you, unihoppy, seems to be: how to keep using a crutch (like a fence) but do so in a way that helps you learn your balance. A fence may cause you to unnaturally stay in a straight line when riding. My own success learning to idle at the fence was limited, because the fence inhibited me from twisting to the right and left.
There is a thread on the forum entitled “My rolling unicycle trainer”. Check it out.
The guy in the picture looks absolutely ridiculous, but who ‘doesn’t’ look ridiculous when they are learning the unicycle (I’m still learning and still looking ridiculous)? If the device works as it should, the rider should be able to steer to the left and right.
I have spoken with and hung out with DaUniGuy. He is pretty clever. Make sure to pick his brain about solutions to your issues.
I started when I was 45 yrs. old, not 66. Even then, I knew that smacking the pavement was not a desirable learning style at my age. The same applies to you.
I hung out with another unicyclist, a very high-level rider, who taught many people to ride. Part of his teaching style is to offer his shoulder to the person learning. For some reason, this does not seem like the most popular learning style; perhaps people feel some kind of stigma in getting that kind of help. Also, the technique of helping is not that easy, and it requires some strength. If you can find a strong, coordinated younger person to lend you a shoulder, that could really help.
Final advice: please ditch the “20 hours” philosophy, which has been popular among some new riders. You are going to have to be safer than a young person, and this is going to stretch out the learning process. However, you possess something all the young riders are lacking: the wisdom of age.
Best wishes!