If you can rotate the shifter itself 180 degrees and you can see the bottom of the shifter rod is bent pretty badly, then you might try rotating and wiggling the shifter until the bottom end of it can clear the shifter rods enough to come out. The shifter end fits into a box formed by notches in the sides of the shifter rods. If the two rod notches are lined up with each other then you will have a box hole twice as big as the end of the shifter leaving plenty of room for the end of the shifter to move.
If this does not work, I would suggest tearing the entire tcase down. It probably needs it anyway. I am not a proponent of violence on jammed equipment. It usually leads to more damage.
I believe that the previous owner, discovering that the t-case was "locked" (read: the bushing had disintegrated) used violent force on the shifter itself causing the end of the shifter to bend. The shifter rods may already be distorted which probably locked the case into 2wd mode.
T-cases are kind of rare finds as folks tend to buy them, regear them and then resell them. You can still find a good one reasonably priced if you look hard enough