Same here. I actually build a similar "3d renderer" and ran into the same perspective "issue" op had. Unfortunately I didn't figure out how to fix that back then. So I actually finally learned how that's solved almost 30 years later. I should fix my QB4 code :-)
Sharing experiences. My first encounter and fascination for these kind of perpective effect was in the 90s demoscene.
I learned to program the magic behind "tunnel" effects by just spawning multiple non-concentric growing circles.