Computer use for 20+ years + the extra cervical rib + forward head/shoulders - can very well be TOS. or even TOS like as in disputed TOS ( no clear cut dx -usually is a chronic RSI)
the CTS could be from the upper issues or called a double crush syndrome.
But if mild rest/time & good PT should resolve it.
Make sure pc/desk area is very ergonomic if still working.

Any particular fingers having more issues than the others or all equal affected?
Index/middle vs pinky & ring?

If you post your area or a large city nearby maybe someone will know of a TOS knowledgeable doc for you. Most MDs are not up on all the nuances of TOS or chronic RSI/posture etc..

But the extra C ribs could be a main player, but a good TOS doc will be able to help sort out if surgery is called for or not.
In the meantime look for upper body posture fixes ,on you tube etc & we have some posted here ( http://neurotalk.psychcentral.com/album.php?albumid=422 ).
Proper /expert PT ( not just anyone) & a very skilled chiropractor should be able to get you started off too.
Make sure they know about the cervical rbs ..