Deadband is not the issue.
Re-calibrate again. Make sure you set endpoints for throttle and brake at 100%. Don't just go as far as the radio allows. When re-calibrated, your throttle should be at full when trigger is pulled all the way.
There are frequent problems getting some escs' into set-up mode when using spektrum. The delay of the system booting up, causes issues. Try it several times if not successful on first attempt. If you still have trouble getting into set-up mode (that's assuming you trouble in the first place), you can use a seperate power supply for rx and disconnect the red wire from esc plug to rx. This can get the radio system booted up before going into calibration mode of the esc.
If none of the works or is relevant to your problem, you will have to re-set your endpoints on the tx, matching it to the high-point of the esc settings.