Mate, so sorry about my delayed reply.
Yes, I do have a different suggestion for you. It's easier, but it ONLY works when your subject doesn't encroach over the edge of your backdrop.
STEP 1: Duplicate the Background layer.
STEP 2: Use the marquee tool to select the first check of undesirable background:
STEP 3: Go to Edit>Fill, and choose "Content Aware":
STEP 4: Press OK and it will fill the area with generic backdrop colour:
STEP 5: Do the same on the other side - select the chunk, Edit>Fill, OK:
STEP 6: Use the lasso tool to select around the subject:
STEP 7: Again, Edit>Fill with Content Aware:
STEP 8: Deselect, then apply enough Gaussian Blur to your satisfaction:
(IMPORTANT NOTE: Your number will be a lot higher than mine, since I was doing this demonstration on the web-sized file.)
STEP 9: Add a mask to the blurred layer, and mask it around the subject. Hopefully you won't need too much precision, but check very carefully that you haven't gone onto the person:
STEP 10: Add the noise layer, the same way you did when you were adding a gradient layer.
Let me know how you go with this.