I am in the middle of doing the same thing and 60 - 120 degree is right for the hexie. And just cut the triangles in half but remember to add enough for the seam.
I made my diamonds by drawing 2 lines, 1" apart on the fabric I am using and then laying my 60 degree line on a ruler along the drawn line. Draw the 60 degree lines 1" apart and this gives you the right shape for the 1" hexie.
Keep space for your seams between the 1" diamonds . I use 1//4" seams so 1/2" or more between the diamonds gives enough space for trimming.
Hope you can understand this for the time being.
I will post some pictures on Sunday. A visual is always helpful.
Please post some pictures of your work in progress. I would love to see it.
peace