No crank, no start, possible immobilizer, ECU?

Ignition wouldn't turn with second key (rare use, couldn't find my keys, used many times before) Had aftermarket alarm/remote start. Lights start flashing and horn, etc. I went inside and found my keys fob didn't work. Removed horn fuse. Normal use key would not turn ignition. Disconnected battery, ended up drilling small hole to access release and get ignition cylinder out, started with screwdriver (horn, lights etc, started as soon as neg. Attached to battery). Moved truck into my driveway, removed "pins/plates" from ignition to get a key to turn it, reinstalled and same outcome, except truck died after maybe 3-5 seconds. (Approximately. 3-5 attempts) Few days later tried some things from YouTube, but now no cranking, all lights, stereo, blower fan etc, work. Replaced fuse #14 and got red light to turn off(dash)horn, headlights flashing stopped. Still no crank. Checked dealer w/vin was told no transponder key req. Removed aftermarket start/alarm no change. I can jump the starter relay and crank, can attach wire to yellow wire at ignition to same pin in relay and get crank. Can do same at fuel pump relay, hear it run. But truck will not start/run, nothing when turn the key to start at all. Any help would be great!