Hi there! First off, good for you for helping this little frog along after what sounds like an extremely lucky encounter with a chainsaw? I call this luck for not being completely splattered.

Unfortunately I can't give any advice on the healing process or treatment as I have really no experience with it. But I do want to say that it's not unusual for healthy Grays to stay in the same spot for extended periods of time. If food comes to you, why bother getting up of the couch when any movement could get you noticed by something capable of eating you?

Another common behavior is to return to the exact same location after a nightly romp- I've found 'wild' grays returning to and spending all their daylight hours in the exact same spot for weeks at a time, so this isn't necessarily indication that she hasn't moved at all (unless you stayed up at night to observe her). If feces is appearing in the cage, and crickets are disappearing, that's really the most important thing.

Are you planning to keep this frog long term or release it after the wound has cleaned over?