Answers to my previous questions:
1-sew batting to back, no need for back fabric
2-yes and no. It didn't look as smooth at I hoped where the envelope closing came together. but keep reading, it worked out to be plenty big
3- I was given permission to remove the current cover from the pillow I was covering. As it was a thick fabric, I thought this would be a good idea, since the place it was sewn up was sticking out.
So after un-stitching the side, I discovered the inside did not contain a pillow form, just stuffing. It was past being able to sew up, so I thought I would try the stuffing in my pillow as it was packed pretty tight. It didn't look good. It was over stuffed and lumpy. So I ran up to the fabric store and got a pillow form. 20" square. The previous pillow was 21", so the cover is a little loose. But at least it isn't busting at the seams. Hopefully my friend doesn't mind.
I think it turned out really cute, and I will have to make a cover for myself - eventually.