The internal oscillator is set @4MHz by default, you can set OSCCON register to go to 8MHz.

As usual i'll suggest you to use a internal Timer (TMR0 or TMR1) as counter. Yes you'll have to use the dedicated pins for that... no harm at all, you have tons of benefits.
1. it runs in background
2. it's more accurate
3. use less code space
4. more flexible

This PIC have this cute and handy CCP module, so you'll be able to generate the PWM signal really easy using HPWM or by setting the according register manually. This also run in background.

HTH