How to wire 2nd light to existing circuit with light and two 3-way switches?
I ultimately was not able to resolve the wiring problem given the current set-up and the wiring in place.

However, I did end up purchasing two sets of https://www.amazon.com/RunLessWire-Simple-Wireless-Switch-Kit from RunLessWire directly ($99.99+s/h each), linked both wireless switches to both relays, removed the existing switches and shorted the appropriate wires, and 2 hours later, I had a working set-up!