The foot can be especially challenging indeed.

Have you had an appropriate sensory/motor assessment? Specifically a neurological assessment?

I would be inclined to see a Physiotherapist concomitantly, as they can possible massage the plantar fascia to relieve any possible tightness of the tissue (not relieved by stretching as the Plantar Fascia does not contain GTOs). Stretching of the specific muscle may be incorporated as well, but should be balanced with equivalent stretching of the opposing muscles (i.e. plantar flexors).