Good / Bad Supplements For dogs?

I was just wondering what supplements / vitamins are good or bad for dogs?

I Have a 13 and a halve year old German Shepherd that has bad Arthritis in his back hip legs, A lump the size of a fist on his spleen and gone blind in one eye with the white glaze now appearing in the other eye.

I have just started him on MSM, Colloidal Silver , Vit C ( Ester c )and Vit E gel caps. Thinking of juicing for him as well.

Also thinking of using DMSO but hear many negative and positive comments...not sure what to believe there?

I have tried him on BARF / Raw diets in the past and he will not eat it...and he lost too much weight trying that diet because he wouldn't eat anything. So that is out.

Cheers

Uly