Why did I spin a main bearing?

All kinds of things can cause main bearing issues. Did you clean the oil passages in the crank perfectly? That's the #1 cause I see of a main bearing failure.

If it IS a main bearing, the rods that get fed by the main will be chewed up too, probably causing the "tight" issue.

High RPM main bearing issues are usually caused by oil starvation/restriction. Rod side clearance will also affect how much oil comes through the main bearing.

But yeah, 2 thou is pretty tight, I'm strange, but I like 3 thou.