Success! I fed the 4500 a generated GPS signal, and once it had a position, it is displaying traffic as expected. Thanks for your help testing the files and getting me going. I generated some additional test traffic from the Stratux to test the various traffic alert states, as well.
What are the thresholds (relative altitude & distance) for normal/proximity/advisory target states in the current software? Testing generated data, I'm not certain they match what is in the v7.4 manual available online.