After making your selection, go into the paths panel and on the bottom there is a button, I can’t remember exactly what it looks like, but when you hover over it it should say something like “Make Work Path” just click that.
You might want to try just saving it as a PSD and not an image file. The only downside I can see from this is a bigger file size, but when dealing with still images this should just be a matter of a few MBs.