Don't use the receiver battery (4.8V) at the same time you are using the ESC. Your ECS will supply power to you Rx. The receiver battery is not needed for flight, you would only use it to power your Rx for testing on the bench, if you did not want to plug in the Flight pack. Never have both batteries plugged in at the same time.
With FlySky, the ESC will be pluged into channel 3, throttle, I believe with Spectrum throttle is channel1.
Regarding servo/ESC wires, red is always positive, the darkest color (black or brown) is negative, the lightest color (white or yellow) is the signal.
Regarding the motor. Do all testing with the prop OFF. The 3 wires can be plugged-in in any order. The motor will spin the correct direction or not. If it spins the wrong direction, switch any two wires. When you do install the prop, the numbers always go to the front, the direction the plane will travel. If you put a prop on backward, you will only get about 40% of the expected thrust.