Final Update (hopefully):

After identifying the problem was somewhere between the battery terminal to the engine bay terminal, I decided to inspect the engine bay terminal first since I recently did work there.

1) Disconnected the engine bay positive jump terminal, under the hood near the driver side firewall. This junction is essentially a stud that is threaded on both ends. One end (closer to the windshield) connects the cable that runs from the battery in the trunk. The other end (closer to the front bumper) connects the cable that goes to the starter.

2) Upon inspection of the junction, there was noticeable electrical arcing on the nut/cable joint on the the windshield side.

3) I decided to test this by simply removing the junction stud and clamping the 2 ends of the cables together. The car started perfectly! That was the problem.

4) Going to take some sand paper to the nut and junction stud and cable ends and clean it up really well.

I'm happy to say I have finally resolved the problem. I learned A LOT during this whole process. The whole process was invaluable but the most valuable take-away was probably a better understanding of performing a voltage drop test under load to properly diagnose (Thanks 80stech). If I did this from the start I would have saved myself from buying a new battery and a new ignition switch. Either way, the cost of the aforementioned was definitely worth the knowledge I gained.

Thanks guys for your help!