Turret mechanically locks into place.
Have you tried loosening the bolts on the tool holders and seeing if they can be moved slightly to align them. It is possible the entire turret assembly is high and this is difficult to fix because negative thickness shims have yet to be invented. I wouldn't worry because a few thou above or below center on a drill or boring tool is irrelevant. In the case of a reamer it could be problematic but reamers should be in floating holders anyway.
Taper of .0002 per inch is okay, not good. If your parts are always short you can probably live with this.
Concave facing is not good but less than .001 over 3.5" is probably livable.
Neither of these can be fixed by parameters and taken together they suggest the headstock is out of alignment. I may be wrong but I do not think these headstocks are dowelled to the bed, just bolted down with some heavy great bolts. You could try aligning the headstock. Machine a four inch length of stock and measure the taper. Then loosen the bolts one at a time and re-tighten them to a bit more than finger tight; I use 'pinky finger tight' which is pulling on the wrench with just a pinky finger. Put a DTI in the turret and traverse along the part you machined; it should show no deflection. Run the DTI clear of the stock and give the headstock a medium whack with a lead hammer intended to move it in the direction to correct the taper. Now recheck with the DTI. If you are lucky you will be able to gradually creep up on something better than .0002 per inch at which point you sequentially snug down the bolts until they are 'whole hand pulling like a maniac' tight.
This is more or less the procedure I used to re-align the headstock on my TL2 when I whacked it out of alignment destroying a tool turret. I got it back to something like 0.0002" over 4 inches.
Incidentally your sighting past a parallel on the concave face is a very sensitive test. I recall way back half a century ago intrade school being told you can see a 0.0001" gap this way.
Now I have any apology, mea culpa, to make. I didn't get the photographs of the parts catcher I promised and I am off again in a few days and will not be spending any time at the business between now and then. I will prostrate myself facing south east and intone "I am sorry".