I agree with ROOT, you're very wise to realize that both of you may not be ready for it. It would be an easier decision for you, I think, if you knew for sure it was over with OW. It seems to be based on what your SIL said -- or at least headed in that direction.
Stay detached -- don't let yourself get attached before you're ready.
Retrouvaille is highly recommended on this site. Have you thought about suggesting it to your H? Now is probably not a good time, but if you have doubts about fully recommitting, or doubt his intentions, it may help.
