Well, the fact that it shows this error about "trigger_allpalyers" tells me it's loading my progs.dat but I can trying changing something else too.

I'm putting it in id1\, inside a progs.pak file and I run with the Ironwail engine (but I believe progs.dat should be supported by literally every Quake port). 

That error message actually tells you the opposite of what you think it does. It tells you about something your MAP contains. The error means the mod you are running does not contain trigger_allplayers - which is probably because you are running the vanilla quake mod and not your custom one.

I would recommend creating a new mod folder under quake called "allplayers", put the progs.dat file in that folder, then run Ironwail with the -game allplayers command line switch. That should ensure you are actually running your custom mod. 

Ah, yes, good point. 

does anyone know how to make working rocket fly sound?

i remember vaguely someone on youtube i think showcased it (but i dont remember the link) so it's possible i believe?

but the closest i ever got was the sound plays on the projectile but either updates too fast (so the sound just keep restarting) or updates too slow (plays at locations that the rocket has long left...)
- as opposed to a looping sound smoothing playing and following the rocket 

Vanilla Quake can't truly do this, produce a sound that smoothly changes location relative to the listener. Anything done in vanilla quake will have been a hack involving repeating a sound. If you were really skilful at the hack, you could create a sound clip that fades out and overlap multiple copies of it to disguise the trick a bit. But it would never be seamless, and a rocket is kind of the worst case because it moves so fast.

The only way to do this properly would be to create a modified engine that included this feature.