on Issue 1: Arduino is configured with both cores already when built, so nothing else is required.
on Issue 2: Could you try to lower the flashing speed? You seem to have selected 921600 and I have seen that to fail on my mac too. Try with 115200 as a safe net and report how that goes. To note, I have had success with many baud rates with FTDI chips, but not the same with others. Silabs seems to be better than WCH, but not quite as good as FTDI.

Source: https://github.com/espressif/arduino-esp32/issues/333