The ingredients look really good. I don't know anything about your vitamin A/beta carotene question, though. I would think it would be okay as long as you follow the dosage guidelines for your dog's weight. A dog I used to have had problems with her leg. She had surgery and the vet started and wanted to keep giving her steroids, injections to put fluid on the joints, and Rimadyl. I started giving her glucosamine with msm (must have the msm). She did great. She still had a limp here and there, but that may be because she eventually got Cushings Disease, which causes muscle tone to deteriorate -- especially in the back legs. I did have to quit giving her the glucosamine when she became diabetic. It raises the blood Sugar levels in diabetics.
In the spring I was going to adopt a buddy for my current dog (until I realized she doesn't play well with other dogs around her toys, if they come near the bed if I'm in it, around bones, etc.) Anyhow, the dog I was going to adopt had one cataract. It concerned me because I am a renter and it would worry me that if she developed bad cataracts in both eyes, it would be hard to adjust if I moved. I did a little research at the time and found a product online that I would have tried if I had adopted her. I think there are a couple different brands, but the ingredient is N-Acetylcarnosine. Do a search for that and read the information on any of the sites. It sounds like an incredible product for cataracts (in humans and dogs).