I know that current wall hung toilets are rated for at least 500 #'s. I am trying to find if that holds true for older (70's) WH toilets. I have reached out to American Standard and Kohler. No answers.
I don't know the weight limit either. They do have them in many public bathrooms though. In my family we had 300 pounds sitting on those. They do make supports for wall hung though.
The Buttress™ Universal Toilet Support is a toilet riser boosting wall toilet stability with over 1,000-lb capacity, adjustable leg, and 20-min easy install.