Looking at that manual for the slide out - not sure they intended that hand pump to drive out the slide out... which would seem kinda stupid. Having said that, I would look at the wiring and see if you can figure out where the 12V+ line comes in from the battery...
Disconnect this 12V+ line (just because your wiring is funky) - using a set of jumper cables hook up the ground to the body of the pump, hook the 12V+ line to that terminal you disconnected the battery line. Then have someone operate the slide out switch and see if it will extend out.
Have a great weekend if you get out in it.
Walter & Donna
2011 CC LB RAM 3500 CTD 6.7L DRW
2013 Cedar Creek 38FL
2014 Days Camping: 35