Honestly I am still of the opinion that this weight reflects the post-burned state of the remains. The facial recon doesn't suggest someone emaciated/extremely thin. If it had said "106lbs (estimated)", then I'd be more inclined to think that they are trying to portray the victim as he was in life. I'm not speaking from a place of certainty though; I don't know how severely this man was burnt.
I went on NamUs to see if giving the burnt remain weight was normal or not... usually if the body is too burnt, they just put "weight: cannot estimate" or give a vague estimate. Some people do have listed weights that seem 'off' though, i.e. this 6'0" guy measured at 133 lbs, 5'7" guy measured at 107lbs, and this 5'5" woman weighing 90lbs. but on the other hand, other people who have been burnt have measured weights that seem very normal for their height! so i can't come to any conclusion
I'm glad that NCMEC is responding to tips, and that James Foster was suggested. I'm not on FB; would someone like to suggest Willie Clark? Or should I do it via NamUs contact? I agree that his circumstances don't back up the ID but his circumstances are so vague in the first place, they don't sway me either way.
I agree that the condition of the remains makes it very hard to take any of the information given at face value. Like you've said, we don't know the extent to which the body had been altered as a result of the burning. I don't know how accurate those reconstructions are. If I'm being totally honest, I'm not even totally convinced that the listed hair and eye color are accurate (in addition to height/weight), but they are really all we have when it comes to narrowing down matches.