recalibrate your transmitter to you esc. when you reversed the channel on the radio you also reversed the esc/transmitters end points. your are gonna need the castle link to turn the lipo mode of since you are using nimh batteries. make sure the battery is fully charged (truck) sounds like you are hitting the low voltage cutoff too. most low voltage cut offs are set to around 6.8-7 volts. try your local hobby shop and see if they have a castle link you can use or if they can do it for you. for the time being, swap 2 of the motor wires and reverse the throttle channel again. that should get you back to driving again.