First, off welcome from Maryland!
Second, you are lucky that you are in Europe and can obtain cloth (officer's wool or broadcloth) that is closer to what an officer north or south might have worn.
The two, that I consider experts in this field, are Les Jensen and the afore mentioned Frederick Adolphus. Both will tell you that it is almost impossible to get wool that is correct for the ACW period, in the states. Our sheep have been genetically altered over the years for one reason or another and believe it or not, the wool is completely different than that of 150+ years ago. Wool back then could have been woven and left without a hem, common on most enlisted US frocks, try that with today's US wool and watch the fun begin.
Much of the wool produced for reenactors from the authentic sutlers, is imported from Britain; I know that at one time Pat Cline would get raw wool from Britain and weave it himself. I believe those days are largely gone.
I would suggest a pattern from one of the older suppliers out there, or the Danish Military museum, I think still has sealed samples from the ACW in a swap over 150 years ago. They might have a pattern or allow you to take measurements.
A good friend of mine stumbled upon a complete and authentic bolt of sack coat blue cloth and the difference, even with the loose weave is remarkable. His wife is a conservator and uses the cloth to repair and conserve museum grade pieces.
Grayrock Volunteer has some very good suggestions as well