tracking down sewer gas smell in bedroom
Is the toilet next to the bedroom or by the exterior wall under the window? If it is by the bedroom you may be able to remove the base board in the bedroom with minimal damage and cost to get access in the wall directly behind the  toilet.  I am going to guess that the vent pipe is cracked in-side the wall and allowing vapors to creep in. 

After making a small hole in the wall smell for stronger odor if so you are in the right area. You do not smell the sewer vapor in the whirlpool cavity because it is probably sealed off from the toilet vent. Repairing the leak will be another issue. One step at a time. Good luck--hope this helps. If toilet is by outside wall then I would smoke the pipes.