These things are as brittle as crayons. Even the 1/2 inch snapped like a pencil. Drywall is probably the only thing I’d go out on a limb to say they are good for.
Yes they are.
Yes. These should work very well on drywall.
Just got this today, I noticed that the hex shank appears to be attached to the bit with what looks like a pin (as opposed to the competitors "pinched" - those divot you see at the hex shank). Sizes 1/16 - 1/8 are secured with one pin; sizes 9/64 - 1/4 have two pins opposite each other. I just cannot tell whether those pins goes through the bit itself. 5/16 to 3/8 the shank are machined from the bit.