We've all been there with the mistakes Hahaha Sometimes you have to laugh or else you'll cry! I've tried to repair several times and finally just gave up even with simple cross stitches!!! UGH!
I'm not sure what embroidery stitches you are using, so.... it might have to be stitch by stitch. Sorry.
If the seam ripper doesn't work, I use a pair of $16 Gingher brand embroid. scissors - the kind that looks like a swan? duck? goose? Hahaha ...that I got for half price!! They are verrrrrrry sharp but with tiny blades to CAREFULLY lift up the thread and cut it (like a razor). I snip every few stitches (usually I use the stem stitch) and then what I can't pick out by fingernail, I use tweezers.
Maybe to avoid any mistakes in the future, try using a water soluble pencil or pen (blue "ink") and double check the design before starting with the thread.
Good luck.
PS: R Y kidding me? $50 bucks ?????????? I don't think so!