Fit issues: on my 3rd muslin, help!

Although I am hoping this third muslin fixes things, I thought it might help to get some comments from people who have sewn this pattern successfully. I have done a FBA, and after raising and angling the darts extra, that area seems to be okay. But the shoulder/arm/neckline has been a huge problem: the shoulder is cut far too wide, dropping almost 2" off my shoulder, and even after cutting it down, there was too much fabric around the sleeve attachment area and the neckline was so wide (seems weighed down by the sleeve) my bra strap is showing. The back bags a lot too. So I am trying cutting an inch out of the center back as well as cutting the top portion of the pattern in a size 4, going to my customized 12, from the bottom of the arm opening, sleeve also in a 4 as it was quite baggy as well. I have never had to change a pattern so much or had such fitting issues. If this one doesn't work I am about ready to give up on it entirely. Can anyone give me advice? FYI...I am using a knit similar to the fabric that I am planning to use: a fairly light cotton jersey.