Sounds like the technical and physical sides of things are pretty good, and you have a putter (well, more than one!) that fits your stroke well, so it seems to me that making any changes in those areas isn't likely to help, and may well make things worse.
What's your mindset when you're over a putt? Are you thinking about holing it (the result) or what you're going to do (the process)? I'm not at your level (usually in the mid-70s), but I've found that I putt better (and hole more putts) if I'm thinking about following my process and putting to the spot that I've picked out rather than the result or what holing/missing the putt will mean for my score. If I hit a solid putt with good pace on the line that I've chosen, that's a good putt to me whether it goes in or not.
I also find that taking too long over reading a putt can be counter-productive - it's very easy to start seeing things that aren't there, or ending up with a read that you don't trust. There's a lot to be said for having a quick look and going with your first impression...