Is it normal that my right testicle is half the size of my left in width?

May be normal: Your notes indicate that you have already been evaluated by a urologist, so I would defer to his opinion. Sometimes there may have been damage to one testicle (the smaller one) or there may be a water collection (hydrocele) or hernia around the larger testicle. Sometimes people are just asymmetric for no particular reason.

No, but: if the testicles, are lying at different angles to one another, it may appear as if there is a size discrepancy, when there is none. An actual 50% size discrepancy wouldn't be normal, so you should see your doctor to get examined.