If you decide to pre-soak, a slight increase in development time will not hurt. 5% should be plenty. If that turns out to consistently be too much, then go back to your previous time. Development times need to constantly be evaluated and adjusted anyway, based on the actual results in the field.

The PMK after-bath is not necessary and time consuming. Eliminate it. It does not add additional image stain and only muddies up the shadows by adding extra overall stain.

Your workflow looks fine, except I would recommend an acid stop bath. Both PMK and TF-5 work fine with an acid stop. I use either Ilfostop or Kodak Indicator Stop mixed at half the recommended strength and use it only one session. That said, if you are getting good results with a water stop, it's up to you.

With TF-5, be sure you are fixing to completion before you expose the film to light to avoid fogging. PMK (and other developers) remain in the emulsion well into the fixing stage and can be reactivated by the alkaline environment of an alkaline fixer. Switching on the white light too soon can result in fogging.

Best,

Doremus