Turtleneck Sweater Design: What to consider?
Don't forget your cuff/waistband design. Will it be a 1x1 rib? 2x2 rib? Something else? And consider the amount of ease you want, not just your measurements and ultimate shape, when sizing. Do you want it to fit tightly? Baggy? In between? And since you're using worsted-weight yarn, you'll want a little more space in the underarm than you would if you were using a lighter yarn.

Also, you could do a raglan sleeve/shoulder the way you're describing it, not just a drop shoulder, so that might be another consideration. (I think raglan turtlenecks look really nice!)

Those cables are gorgeous. I really hope you'll come back and post your finished product.