Difficulty In choosing sprokets

Not sure why you imagined you would suddenly be faster than people on road bikes. All of them have the ability to gear much higher than you and won't even need to be able to spin.

Pain in the elbows on short distances is sometimes an indicator of an off sized stem. Where is the pain, inside or outside.

I was getting pain in the outside of the elbow to the lower ligaments of the tricep...

I have got a 50 cm frame with on one midge drops and planet x stem i am about 5'8-9'' and normall regular trouser length and shirt arm length if that helps?