Sorry to hear about your condition. Yes, I think there is an easy way to calculate a number that you can use. On average, there are 2.5ft to a single step and there are 3ft to a yard. Would you say your average step is say, half this due to your limp? If so, simply double the number of steps you need to make the same yards outlined above. Make sense? So, your step, in your case could be 1.25ft.
So, based on the numbers above, the standard units say, its 25 steps to mark out 20yds. For you, if your steps were half that of the standard units, then its 50 steps for 20yds. Does this sound reasonable, or are your steps, smaller / larger than half the standard units (i.e., one third or two thirds the average)? I can calculate more exactly if you would like.
I cant help with the walking in circles!!!!!
I can, leave the drinking beer until after you have been shooting!