I need help finding an affordable archtop
If you liked the Joe Pass, get it and make incremental upgrades to it over time. What's your teacher's definition of a "good" guitar?
They're pretty simple machines, really. There's not a lot that you would need to do to improve it considerably. New pickups and electronics (i'd suggest Bartolinis... ever heard Tuck Andress' tone?), maybe some higher-quality tuning machines, maybe a high-quality compensated bridge, but that's about it. If you like how it plays and how it sounds (especially unplugged... that's the test of how resonant the woods are), improving a fundamentally "okay" guitar is pretty straightforward.