I figured it out how to disable the reverse cut out, thanks to everyone on this forum!!
Here's a little more detail on how it's done (The bend the thingy out of the way method.)
Get a pair of pliers or a RoboGrip.
Turn the wheel all the way to the left.
Shut off the mower
(in case any lawyers are reading this)
Drop the deck as low as you can get it
Get on the ground on the pedal (right) side and look at all of the connecting arms that connect to the transmission.
Rock the reverse pedal back and forth. On the inside of the frame, on the opposite side, look for a ~3 inch long, gold color, triangular shaped piece of metal connected to the steel rod towards the center of the tractor. It moves back and forth as you rock the fwd/rev pedal.
At the end of this triangle is a metal tab that depresses a silver, metal button connected to the frame. This was what cuts out the PTO when you back up. Use your pliers to bend the end of the triangle-shaped piece out of the way enough so the tab no longer contacts the button.
I've only put about 7 hours on my 2518 since I got it (with 123 hours on it) and the connection harness at the end of PTO plunger actually broke from having to restart the PTO everytime I needed to back up a foot or two. For now I have some electrical tape holding the end of the switch to the harness, but this is only temporary. I'll make a separate post about this issue later, but if anyone knows how to permanently fix this I'd appreciate it.