At 6 weeks the arms and legs are still just "buds".
Fetal development: The first trimester - MayoClinic.com
By 8 weeks the fingers are
starting to form, but it is almost impossible to see on an ultrasound
What your baby looks like -- 8 Weeks | BabyCenter. At 8 weeks the lower torso hasn't straighten yet and the head is still misshapen, so it still looks likes largely the same as a chicken embryo at the same stage.
What are the basic Christian teachings on this subject? I don't see much of anything in the Bible that clearly addresses this issue.
The majority of Protestants are pro-choice, as are 70% of Republicans. The majority of "main line" Protestant churches are pro-choice and the only countries I know of that have ever banned abortion are Catholic, not Protestant. So it hardly seems like a clear cut issue to me. Most Protestants disagree with you on this subject. This is not because the Bible has a clear message on the issue, it has a very ambiguous message.
The word nephesh is translated two thirds of the time as soul, one third of the time as spirit, and then there are 40 or 50 of the 750 occurances that are translated as everything from perfume to dead body. In Genesis even
fish are said to have nephesh. Nephesh is not much like the clear cut distinction between soul and spirit that is put forward in the New Testament. Once the line between soul and spirit is blurred, I think it is easy to blurr the line between body and spirit, which I think is the crux of the problem here.