You go!
The thing is with our seams is that any mistake is double by virtue of being two pieces of fabric. The other thing is the number of repetitions. But to take away fullness in a border more than can be eased in, start by reseaming just a thread away from a current seam. Skip one repetition and do again. Check every seam to make sure when you have taken off enough -- even without vision issues you don't want to try and take out two seams right next to each other.
Again, I'd also stress that this indeed is an advanced border treatment. It is much easier to make the border fit correctly a bit larger than the top and make it fit with a coping strip.
Looking at it today, I'm agreeing with the others who say you just need one more narrow color band at the end of your border and then fitting it in.
I've tended to sew a bit scant and have to trim down my units periodically. But with my new machine, I'm being a bit fuller. Because of my vision issues I'm not doing things that require serious precision any more, but it is a noticeably thing and I'm having to relearn/adapt.