Good write up & a nice deer with your Single 7. My results were a little different than yours but one or two animals doesn't make or break any caliber. I think any time you use a small caliber it's more what bullet you use than what caliber. Also, shot placement is always a factor, nothing makes up for bullet placement & I see where you said your shot was off just a bit.
Maybe if you had hit that heart you would have made a one shot kill & your conclusion might have been that the 327 was up to the task.
A few months back I shot a doe antelope in Utah with my iron sighted 327 at 73 yds as she stood broadside just behind another doe in an open CRP field. My bullet was a powder coated 135 gr Ferminator HP running a bit over 1500 fps. The cast slug got both lungs & a rib on both sides with an exit.
She got turned around & maybe took 2-3 fast steps/jumps & dropped. Not a true sample with just one kill on my part but I was both happy & surprised at the results. Would I use it again, for sure I'll use it next year just for comparison.

Dick