How much oil should my Six be leaking?

You need to determine how much of the daily loss is from leaks and how much is burning. Put a newspaper under it to monitor the leaks. I have several cars that are usually wet underneath, but they leave few spots and use negligible oil. A little oil can hang around a long time. I just keep a metal pan under to protect the driveway. My Mercedes are always wet and diesels have the blackest oil. Indeed, I can't recall owning a car that didn't leak oil within 3 years of being new. Worst was my 2.4L Plymouth. It leaked oil from the head gasket to outside, which was a design problem I fixed only by installing an MLS head gasket.

Trannys usually leak from the bottom pan. No big deal since it needs to be removed every ~100,000 miles for a filter, fluid change, and band adjustment anyway. They can theoretically leak from the front shaft, but I haven't seen that. Good since fixing that requires removal. If you over-fill them, they will burp oil out.

Good you don't have a bottom engine shield. My son's Chevy Cruze has one, with a current recall. Seems quick lube monkeys spill oil, which has caught fire sitting on the shield.