Permethrin is not considered effective against SLM according to my research.An alternative is to get a Permethrin spray and spray his legs and feet. You'll need to do this again after 7 days as well.
Ivermectin is effective but expensive unless you already have it on hand or able to get a small dose shared from other local livestock keepers.
https://the-chicken-chick.com/scaly-leg-mites-in-chickens/
It works by suffocating them.thank you i’m taking the Vaseline approach for now
I haven't had SLM.. but my feather legged birds (especially roosters) did get some damage similar to the redness you have going on from feather mites or lice of some sort.. which WAS treated with the permethrin spray mentioned by the other poster.
He's handsome.. maybe a bantam Cochin cross if he's four toed.