Sounds like everything is wired up backwards. Swap a motor lead and reverse your channel 2. then recalibrate.
Your using reverse for forward and forward for reverse. And it sounds like its set at 50% reverse speed. It should run faster in reverse as is. Red led means it is receiving a reverse signal from TX. Green leds means a forward signal is being received.
I don't recall the size of fan but these
fans are a good replacement option.