I don't think you are over training, I think you are over trained. There's a difference. I would recommend that you take at least one week off from all targeted exercise, just keep the half hour walk at lunch time. You have worked out consistently for 26 years, and guess what, even highly conditioned athletes take weeks off as part of their training, every year. Heck, you have so much fitness stored in the bank you could probably take a month off and benefit from it hugely.
I agree with the other poster that you need an intense course of flexibility training right now. But I also think you could do with booking a couple of sessions with a physical therapist and ask him or her to take a look at your lower body and check for muscle imbalances. This could be what is causing your shortened range of motion and tightness in the hamstrings. You need to sort this out rather than continue to weight train on legs whose muscle ratios are already out of whack. Otherwise, next stop, injury.
It's not that your body isn't in good shape, it just needs some tweaking and fine tuning. You sound like you need a different sort of training, and we do, as we get older.
You also don't need to be doing cardio 6 times per week and full body weights 3 times per week. If your cardio workouts are intense, you can cut them down to three per week and not lose any cardiovascular fitness at all. Instead, schedule in three extra sessions of yoga or whatever special training the PT thinks you need and extra rest and your aches and strains and tiredness will be thing of the past.
Clare