Hey birdie!
[ I am not any sort of medical professional, but I have dealt with a lot of doctors and a lot of tests. So here are just some humble comments based on my personal experience and research. ]
First...when did you get tested for Carpal Tunnel Syndrome? I assume you had the EMG(where they shock the crud out of you). I think my CTS progressed pretty fast, so if it is convenient, and if it's been a while since you were tested, you might consider getting rechecked.
When your finger joints lock up, does it feel like the joint is physically stuck, or is any of the problem that your finger muscles don't want to work properly?
If your finger joints are swollen or red, that sounds more like an arthritis thing. It can affect how well the joints move. A Sed Rate is an easy blood test they can do to check for inflammation, and I think it is fairly cheap.
As for the numbness. Numbness is almost always caused by a nerve problem or a circulation problem. Is it only certain parts of your hands that go numb? CTS mostly affects the thumb and first two fingers. When mine was bad, those fingers would go numb just from me holding my elbow loosely bent. If your other fingers go numb, but NOT the thumb and first two fingers, it can imply that the problem is at the elbow, not the wrist. There is another nerve "tunnel" at the elbow...right where it burns if you "hit your funny bone." If you've done that, you will feel a zap down from your elbow into those last fingers.
If you are also having spine problems up at the cervical/neck level, that can cause pain or numbness in your hands, even if there is none in your arms. Most neurologists I have been to never seem to consider that possibility--only if you have pain radiating from neck to the problem area. For example, I have some major neurological problem in my left hand, and a pinched nerve on the left side of my neck, but I can't get a neurologist to think they just might be related!
My advice: make a list of questions and concerns, then either make your doctor(s) address them or find the answers yourself. It is so important to go to doctor appointments as prepared as possible so you can be in control of your health care.
Please feel free to ask any and all questions here. We have so many people that can help. :)