Question for my dad: he wants to get some joint supplement, he do not suffer any joint pain/do not exercise a lot just once a week, what content of glucosamine should he get? W msm/chondrotin sulfate? Thanks!

Exercise is better. There are many ways to exercise. Walking is a great choice. Normal joints are kept healthy by using them. The cartilage is helped by loading, by use, by movement. Supplements might help some folks, but my advice, based on what you wrote: encourage him to exercise! perhaps you can do it together.
Chicken collagen-MSM. Glucosamine and chondrotin are both in a good absorable form in chicken collagen taken with msm 3000mg two times a day, the chicken collagen provides the building material and msm stimulates the healing. B-6 ( provide amines) needed in in the healing process. Levels of b-6 are tricky since a high levels can be the signs of inactivity, and Niacin level(product of b-6) can be used to measure activ.