1) I work in Engineering for Spektrum, and this would have crossed my desk but I do not recall it. I need your telemetry log file (.TLM) and your model config file (.SPM) so understand your settings.
2) -85dBm is about the range at which your receiver will not provide telemetry back to the transmitter. That's why that's the default value. If you lower the dBm value, you may be out of range before you know it. The -85dBm value is approximately 40% of control range.
3) Yes, the handle is the telemetry receiving antenna as well as one of the two control antennas.
We have several Service Centers around the globe. You can send it to them and ask them to forward it to the USA Engineering department. I communicate with most of them for issues. Send it to your nearest one.
Andy