Fitting Help – Shoulders & Back

Hi Everyone, thank you in advance for your help! I’m on my third muslin now for the classic shirt and I’d love some input before I go any further. I’m relatively new to sewing and pattern adjustments, but have taken a few pattern alteration courses this fall so if I only know which adjustments I need then I think I can make it work on the pattern! Here is an overview of what I’ve done: My measurements are B/W/H = 35.5”/30”/38” and I’m 5’10” so I chose Size 6 to start with. My high bust also measures 38” so I used the A/B pattern (even though I’m a C cup). Having taken a bodice pattern course and knowing my shoulders are broad, I measured the pattern shoulder width and mine and decided to increase the shoulders via a broad shoulder adjustment by 5/8”. I also increased the length by 1.5” (and have since decided only 1” is needed). In the first 2 pictures you can see this muslin. Since I have never sewn a button up before I went through most of the steps for practice (I also pleated the back the wrong way in this one…oops!) I should’ve pinned all the way to my neck, but the shirt was very tight through the upper back and there were diagonal pull marks from the bust through to the shoulder. I then thought that perhaps I made the shoulders too wide, so I re-set-in the sleeves to what would be the equivalent of only having added 1/8” to the shoulders (this was rough to see what would happen). I still had fit issues (pictures 3&4). My third attempt was to cut a size 8 to give myself more width through the shoulders and back. This is the third muslin (pictures 5-7). I graded to a size 4 beneath the front darts and I’m happy with the fit through the waist. However, the main problem I continue to run into is that the sleeve cap is restrictively tight, the yoke is tight, yet the back bodice balloons out and is totally unflattering. Also there are drag lines in the front shoulder area and I feel as though my shoulders are being pulled inward. My thoughts are that I should add back in a broad shoulder adjustment and that perhaps I need to adjust for a square shoulder. I think a C cup may also help. The part I’m stumped on is what to do about the back yoke and bodice and how to rectify the tight sleeve cap. Any and all help would be so very much appreciated! I’ve also included pictures of ill-fitting button up shirts currently hanging in my closet from box stores.