I don't understand why you don't want knee replacements. I'm 70 and had both knees replaced when I was 67. I too was bone on bone. All the pain is gone, I go up and down stairs with no problem. Joint replacement is extremely advanced. Why bother with the pain and ineffective treatments?

It's up to you of course. Unless there are other reasons precluding it, you sound like a great candidate for knee replacement.

And your weight is on the high side, but not that high. What does your surgeon say?

Finally, it's great that you swim. Do avoid the breast stroke as it is very hard on the knees to kick out at an angle as required by the stroke.