How do you stop your bike? You said that you have to be above 3.5 mph to "stay upright". That implies that you fall over below 3.5 mph. I can take you at your word that you can't stay upright at 3.5 mph but I fail to see how you can deal with stopping the bike if that is your standard. Stopping a bike implies hitting 0 mph at some point which says to me that you don't fall over when you hit 3.5 mph so you have the skills necessary to ride slower than that speed and just need to work on them. I suspect your "3.5 mph" standard is more a psychological limit than a physical one.

No red herrings, just common sense.