What is the flying weight? That will help calculate what load are on the motors in a hover when the details are put into ecalc.
It does sound like something is overheating. It could also be a bad motor or a bad solder joint. Try swapping esc's one at a time to see if the problem motor moves with the esc in question. If it does then the esc is the problem. If not then try swapping motors and see if the problem moves with the motor. Failing that check your solder joints and connections.
If you loose radio the copter will just drop out of the sky (unless you have a failsafe settting set). With the antenna the last bit sticking out the end past the shielding is the important bit. All the rest does not do anything but is there so you can get the important part where it will pick up signal best. It is worth mentioning that this end bit must be straight. Also, if you have two antennas they should orientated 90deg to each other. This is for diversity. The end of the antennas don't transmit or receive much signal at all so you don't want either the transmitter or receiver antenna pointing at each other or you will most likely loose signal a distance. This is why you put the two reciever antennas at 90 deg to each other because if one antenna is pointing directly at the transmitter during the flight the other antenna won't be. This is also the reason you see people's radio antenna's pointing sideways. Most of the people will point their transmitter at the aircrat they are flying so putting it straight out is the worst place to have it.
A quick little search on Youtube found this. It gives a basic understanding of how atransmitter antenna works. The receiver antenna works the same way.
http://www.youtube.com/watch?v=lbo_cvYpj7Q