Yesterday, I found a much better thread for this quilt. The greens are lighter, and there's more yellow. I got a second thread too, one with only yellows. The green/yellow one is in the left fan. Hard to see in the photo, which means it's somewhat more noticeable in real life but still muted. The partly done fan on the right has only the yellow thread. This is really subtle, and I plan to use it only here and there.
Still stitching with my left hand. I've included using a quilting spoon. It was awkward at first, and pretty discouraging to have to figure it out---it felt like a major regression---but it eliminates underneath-finger pricks, use of fingernails to move the needle, and sideways pressure on the fingers---all worthy things to avoid. I can tell that I'm relaxing more, knowing that my fingers are much less likely to get poked. Another benefit is that it actually works and works well! It certainly does a great job on the stitch length I'm aiming for, and I can see potential for standard short stitches, too. Heaven knows what it's doing to the tip of the needle, but so far there's no noticeable effect.
I see definite improvement in stitch quality and am hoping for a speed increase soon. Right now, I'm somewhere around the 4 or 5 hours per square foot rate.