I think you are way over-geared. With the high speed idler, 1717 motor, 22/44 gearing and on 6S you are geared for over 70mph and that is before you factor in any tire ballooning. Way too much I think and the amp draw from the heavily loaded 1717 motor would be pushing the MMM to and probably beyond it's limits. If you don't believe me enter your setup into the Speed calculator on Scriptasylum.com and you will see. Drop your pinion to 18T and you should be geared for just under 60mph which I think will fix the overheating problem.

Also Deans (even worse fake Deans) connectors don't really cut it in my book when it comes to high draw applications. For a setup like yours the Castle 6.5mm bullets would be much better.