Personally I would not do surgery on a 3 yo with grade 2. Patellar luxation is SO common. BUT, there are ortho surgeons who might recommend it because it stabilizes the knee and prevents wear and tear on the ligaments.
I would try my best to prevent him from jumping on and off furniture....get ramps and/or steps. I have both and most of my pups use them. I have one who thinks he is superman and flies off the bed. Work in progress.
There are quite a few informational posts here on YT about patellar luxations and cruciate ligament tears (also common in yorkies) due to wear and tear on the ligament due to patellar luxation.
I have never seen a dog limp due to patellar luxation...sometimes they will pop out and pop back in. If you really want to have more in depth knowledge about this, I highly recommend you see a board certified orthopedic surgeon....and one who is very experienced with knees.
www.acvs.org