A healthy weight for him? Wow, that's tough. At 7ft...........I'm guessing 15lbs, 20 max. And that's a wild a$$ guess. Look at the size of his head in comparison to the rest of his body, if his head looks too small or too large for his body, he may be over/under fed. In the one pic you have of him, he looks good to me, but that isn't the best pic to try and judge from. If you have or can get other pics, post them.

Other than obvious signs of neglect or poor husbandry (dirty cage, multiple retained sheds, wheezing/whistling breathing caused by RI) it's hard to "Look" for signs of ill health in a snake. I'd recommend you take him for a vet visit a soon as you can to check for internal parasites, etc. In the meantime, keep him quarantined away from your other scale kids.