I decreased the frequency of PWM by including following code in void setup() TCCR0B = TCCR0B & 0b11111000 | 0x05;
This decreases the frequency of PWM to 61 Hz and made a minor change in circuit (circuit attached)
Motor is able to run at pwm value 50 and above. But it vibrates alot. The good part is, TIP is not heating. 
What other changes can I make?
