" If my pfsense box had been installed right after the cable companies modem so that the pfsense WAN address had been set by DHCP (76.26.XXX.YYY), would my default route have been the 192.168.3.1 address?"
Yeah with stephen only speculation - you clearly were dicking around to get a gateway set to your own address… In a typical setup where you were directly connected to your ISP.. bing bang zoom you would of been dhcp on your wan and default 192.168 address on your lan and not have had to touch anything and would of been working out of the box.
You playing around with static on wan and changing the IP on your lan interface is where you prob got messed up.
There is RARELY a good reason, and I mean RARE!! to double nat - its pointless, it is a performance hit, and yes somethings are going to have issues working with it, and is just a PITA all the way around.
I would suggest you want to use pfsense as you firewall/gateway then use it as intended - if you need more than 1 network segment/vlan on your lan side then add nics to pfsense to allow for that vs using routers that nat as your way of creating isolated segments.