99 was jamming. Loved the guitar tone too.

I think you are pretty much right on the mark.

Compression and a fast mild echo. I also think there's a small room verb on it. It has a right in your face, small room, ambience to it. None of the fx used are used excessively or in a heavy handed manner.

The choruses are layered with tight harmony and very likely doubling since it sounds so much fatter. The doubling would account for the "chorus" effect you mentioned.

Very few people intentionally put a chorus FX on the vocals. Not saying it isn't done, just that very few really use that. You get a similar, fairly pleasing, chorusing effect naturally, from layering multiple takes of the same vocal line that are actually sung vs cloned.

You can find my music at:
www.herbhartley.com
Add nothing that adds nothing to the music.
You can make excuses or you can make progress but not both.

The magic you are looking for is in the work you are avoiding.