which is too long for the RESET pulse of the arduino:
There is no such thing as a reset pulse that is too long.
DTR is low all the time the serial port is active. The capacitor turns that level into a pulse, if it did then the arduino would be held permanently in reset, maybe that is what you mean by too long? It is also pulsed again when the serial port is deactivated, so a reset happens then as well.