You have hit the nail on the head Jamie-very perseptive analysis from
just a set of pictures.
We do have wheel spin and one factor is probably the hard rubber on
the wheels and also the tread.
Another factor is that the Robot is very front heavy and thus the
weight over the back wheels is too light.
The sprocket ratio is around 4 to 1 and altering this is possible
but as you deduce -not an easy task.
The distance between the wheels will have to remain-it would be easier
to cut off the front jaws and have a lightweight heavy than to alter the
wheel spacing.
Conclusion-Fixable