1) With any activity you will run the risk of further deterioration of the knee. Sitting down to go on the toilet multiple times a day could result in deterioration faster. I know, I know, silly/stupid example, but that's just my personality. It all comes down to risk vs reward. Higher weights will place higher stress on your joints, but I don't think that it will necessarily be the higher weights that will drastically accelerate deterioration of the knee. It will be more technique based IMO. You may have to alter specific exercises that you used to do; examples include reverse lunges instead of forward lunges, keeping a more vertical shin during squatting movements, limiting high impact activities that will stress the joints higher (box jumps, depth jumps, etc). I look at the situation this way, even if you use lighter weights you will still have higher reps, and if you continue to use a technique that places higher stress on the joint, you will be still be placing a high stress level on that joint.
What are your goals? If your goal is to look and feel better and be able to play a pickup flag football or basketball game, then you need to determine how much load your knees can take in a given time frame and adjust training accordingly. It will be a lifestyle change as well - proper diet to help with inflammation control, healthy lubricated joints, etc. I will not try to say that I know more than just some basics in that field, so people like Johnny Bowden, Brian St Pierre, Berardi, etc would be the resources to look into.
2) My current credentials are MS, ATC, LAT, PES, CES. What does that all mean? I have my masters in science, did my under grad in Health Science - Athletic Training, am a certified athletic trainer (not personal trainer), am licensed in the state of florida for athletic training, and continued my education to get my Performance Enhancement Certification and Corrective Exercise Specialist certs from the NASM. I honestly don't feel that means shit, and my experience provided me with a lot of knowledge. I did my undergrad and graduate school at BCS schools and and worked with many collegiate teams, the bulk of my experience coming from football, swim/dive, and baseball. Then went onto work as an Assistant Athletic Trainer at a 1AA school where I was mainly working with Football and also covered baseball, cheerleading, and golf. I currently shifted gears and work in the high level Performing Arts.
3) Resources I would recommend include Bulletproof Knees.
Hope this helps and best of luck. Again, even with people's expertise and background, always refer back to the physician you are working with and clear all activities through him/her. We are unable to physically evaluate you and everything suggested is based off of assumptions of your situation.