I agree mites are the lesser problem (unless they are the cause of the sores on the hocks). After his next soak, can you apply triple antibiotic ointment?
Oh my. Poor guy. He does appear to have scaly leg mites, but can’t imagine it causing those sores up above? I definitely think a nice warm epsom salt soak would do him some good. Treat the mites by smoothing in oil (coconut, etc. or even Vaseline).