Suburban SF30 furnace problem

Kinda need some direction here.... My furnace operated fine all last winter but started to act up nearing warmer temps. Since the temps are getting lower here in the PNW, i have been trying to get the furnace back up and running.

When it worked properly, you would turn it on, the thermostat would call for heat, the blower would start about 10 seconds later, then about 20 seconds later you would hear a "pop" sound and then the slight jet engine sound of the burner working. As winter went on, the jet engine sound got fainter and the pop turned to a click. It also seemed to not be as warm as it had been before.

Then, it got to the point where you would hear the click, feel some heat, then, 2 minutes later, it would just blow cold air.

Now, the blower starts after the delay, no click...pop...whoosh or anything else. Just blows cold air as long as the thermostat is set to heat.

Heres what i know:
I have 13v to the furnace and a good ground
I have a good signal from the thermostat
I have good airflow and fan speed
Sail switch is operating and works as designed
Propane supply is getting to furnace
Delay switch is operating properly

Thats as far as ive been able to go so far. Anybody have an idea of what could be happening? It seems like its just been progressively heading towards failure. Thanks in advance!