No one makes mistakes . . .
. . . if they stay in bed all day! Hey, ol' blue, you stepped up to the plate and that's what matters most. I'd still give Batson a call. They may have a section that'll fit properly and then you'll be able to start over.
You already received good recommendations. I'd try to removed the seat by heating it. If you used 2-part epoxy, it should be fairly easy to disassemble.
One of my favorite mistakes is when I heated up a metal reel seat (already on a blank) over a gas stove to remove it and when pulling it apart, grabbed the seat with my bare hand. OOOOOOOOOOOOOOOuch!