I cut the facings way too narrow. The buttons with the lace around them simply did not fit any way I tried it. There was only one option left. Ordering more fabric, and re-cutting all yellow parts.
Burnley and Trowbridge had a lovely yellow wool broadcloth for $25 a yard. It's lighter than my original color, but still in theme. I just used the IXth infantry grunt uniform for reference on the shape and width of the collar and facings. It's much wider than my original eyeballing, and you can barely tell on the color difference. Next up is handstitching buttonholes on the cuffs. I double-layered them in the yellow wool, and they were too thick for my puny machine to handle. I also added a buttonhole. The IXth uniform description calls for four buttonholes on the sleeves, but it just looked more balanced with five. Now I just have a lot of handsewing to do, and this project will be done.