Update!!!
They have the parts now for the timing chain, but "the" "mechanic" has again emphasized that the clutch is "sticky". However!!! Since I have been a patient and understanding customer (real talk: I worked retail. unless you are insulting my intelligence I am not going to blow up on the phone) they are going to do a complimentary clutch replacement at the same time, and they're going to extend the warranty an unspecified amount (otherwise it would run out before I get it back). They are ordering the clutch and it's going to take 7-9 business days to arrive.
The clutch replacement is interesting, for a couple reasons - one, there are no cheap aftermarket clutches for the ATS, so it is going to have to be OEM parts. Two, I still don't think there's actually anything wrong with the clutch... so replacing it is either going to prove that, or the car is going to start magically driving better.
As for me, I have access to other vehicles (and two plated motorcycles) so I can continue to soldier through this. I will admit I have been experiencing deep regret over ignoring the advice I received to walk away from this, ignoring common sense, and my gut. But hey! I'm losing less sleep over it and my weight is coming back up, lol