Controlling DC motor using the Servo pins
No. A servo motor has its own built-in driver and you just send a low-level PWM signal to control it. That cannot directly drive a DC motor.

If you want more DC motors you will need more DC motor driving hardware.  For simple speed control in one direction that could be as simple as a NPN transistor (or N-channel FET), a base resistor, and a flyback diode (just like driving a relay). For direction control you will need a H-bridge like the L293D (which incidentally is a very poor choice of driver by today's standards - very inefficient and lossy. I wish people wouldn't persist in selling it.)