found old quilt blocks
#4
I've seen similar blocks put together with neutral or white squares and triangles inset between the diamonds. These require "Y Seams", which may be why the units were never finished. Is the fabric thin and loosely woven? Might be a detrimental factor to working with them, unless you really love them or they hold sentimental value.
#7
Here is a blog tutorial that you could skim through to the part about setting into the background. http://hopefulhomemaker.com/2013/04/...lock-tutorial/
#8
I think I would put a piece of muslin on top, sew around, leaving an opening, then birth it. Press well and machine applique or hand if you want onto the background of your choice. that would give some of those fragile edges some support and cover the seams at the same time. (can you tell I would not want to deal with Y seams?!)