I have had enough problems with my steps that I have actually learned enough about them to fix several problems. What you're experiencing is similar to a problem I had.
The steps are basically made up of a control system, gear assembly, and motor. The control systems sets direction and the motor runs until it senses force.
If you're steps are stuck at the halfway point and they're not making any noise at all (clicking or humming) I would start with checking power, grounds, and switches. Next I would check the motor. You already know there is power to the steps because of the light so you just need to get a meter and check in that area.
The only way I know of to move the steps manually is to unhook the gear assembly (its quite easy to do) and you then simply move them back and forth with your hand and temporarily wire them up for travel.
When working around the steps you need to take precautions as you don't want them moving when you're under there. There is quite alot of force from that little motor when run through the gearing mechanism that could cause injury.