I understand he doesn't handle well, but he may be having difficulty getting the sheaths off the feathers - any that you see on the neck that look loose or ready to come off you can try helping him out. I've seen where some have to help their Silkies.
If I remember correctly without going back an re-reading your previous threads, he is quite advanced in age (8yrs) and it's not well understood what's going on with his legs - gout, arthritis or other - I'm sure it's heartbreaking to see him struggle with balance and getting back up.
Does he seem to eat his feed well without adding anything extra? Chickens are sometimes suspicious of change up in feed - the cat food is a good idea along with tuna. I am all for trying natural remedies and a lot of people use them - I think they can be very beneficial to health and healing, but your main goal is to provide comfort/supportive care for his remaining days, so if adding herbs/spices prevents him from eating well, then lessen the amount use, try one thing at a time in a small amounts or eliminate them all together. Hopefully @Arya28 can point you in the right direction on those and help you find the right "formula".
If I remember correctly without going back an re-reading your previous threads, he is quite advanced in age (8yrs) and it's not well understood what's going on with his legs - gout, arthritis or other - I'm sure it's heartbreaking to see him struggle with balance and getting back up.
Does he seem to eat his feed well without adding anything extra? Chickens are sometimes suspicious of change up in feed - the cat food is a good idea along with tuna. I am all for trying natural remedies and a lot of people use them - I think they can be very beneficial to health and healing, but your main goal is to provide comfort/supportive care for his remaining days, so if adding herbs/spices prevents him from eating well, then lessen the amount use, try one thing at a time in a small amounts or eliminate them all together. Hopefully @Arya28 can point you in the right direction on those and help you find the right "formula".