Well, I'm on the third muslin. I think it's getting better. I went down to a 14 in the shoulders, 18 in the armsceye and bust with a FBA. Also did a dowager's hump alteration. This has made a huge difference.
The sleeves and back are still waaay to tight. According to Allyne Bane's Tailoring, the tightness in the back is caused by not enough ease in the bicep. You are supposed to have 2 to 3 inches of ease in the bicep of a jacket. I had only 1 inch. The shoulders were still too long and back too wide (and tight). Added a half inch on the top and bottom of the sleeve, trimmed the shoulder down by 1/2 inch and put new (bigger) sleeves in. The fit is much much better. We're getting somewhere. Also had to add 3 inches to the hipline.