Thanks for the reply, sitloongs.
I have an regular ISP connected to the WAN port of the BR1. The router is then connected to LAN port 1. ISP Pass Through is set for both the primary ISP and the cellular network. Looking at your examples, it appears they mostly relate to when the BR1 is operating via the cellular network. I have looked at connecting to the BR1 thru the router when the primary ISP is operating but I have not figured that out as I do not know what the IP address of the BR1 is during that stage. To do the other methods you are suggesting, it appears I need to disconnect the router to have my computer pickup the pass through IP which would shut down the LAN.
Am I missing a step or a critical detail in order for this to be successful?