Help needed with shoulder adjustment please

I could really use some help with a forward shoulder alteration on the Fira dress. This is my first Liesl and Co. pattern although I’ve been sewing for 50+ years. I’m making a straight size 10 with an A/B cup. I’ve made a muslin, although it wasn’t intended that way at the start. (I should have known better!) I lowered the bust darts an inch before I started. The dress fits really well in the front. I love how it looks and hangs - shaped, but not tight. The back however has some strange wrinkles. Upon investigation, the shoulder seam is about ⅝” back from where it should be.I tried adjusting the dress forward on my shoulders and the back wrinkles vanish, so I think this is the problem. I don’t usually need to do a lot of alterations and I’ve never had to do this adjustment before so I may be missing something obvious. I read Lyndsey’s blog post about doing a forward shoulder adjustment and I understand what she is doing. She adjusts the shoulder seam forward in a wedge shape leaving the neck edge in its original position. I don’t think this will work for me as my shoulder seam is too far back at the neck edge also. At this point I get confused.I see examples in my books about forward shoulder alterations that include the neck edge, but they're all on garments with a straight shoulder seam. The Fira has a nice rise at the neck edge and the shoulder seams aren't straight.I can't figure out how to cope with that. I started by cutting off the seam allowances on both yoke pieces. Then I spread the shoulder seam on the back yoke by ⅝” and attempted to reattach the seam allowance. The seam allowance is too long and I don't know how to handle that. If I match it up at the neck edge, it is about ½” too long at the sleeve edge. I can probably redraw the sleeve edge, but it feels wrong that I'm losing that ½’. If I match it up at the sleeve edge, I'd have to redraw the neckline - no idea how to do that! I don’t want to mess up Fira’s nice raised neckline! I lowered the shoulder seam line on the front yoke piece by ⅝” and reattached the seam allowance, which worked better than the back yoke piece. Am I missing something? I’m hoping I can rescue my “muslin” by removing the yoke and attaching a new one with an adjusted shoulder seam. Any help would be much appreciated! I’d really like to solve this so I can make some more Firas. Thanks very much, Kanatajj