If the deemed medical professional, who should be a MD, was not appointed by the officials prior to the start of weigh-ins, the last call should be in the hands of the officials, who are trained to do skin assessments. A sports trainer is typically not a physician. RNs and/or NPs sought out for opinion under such circumstances should not be credible decision makers in a situation of this nature either, for they are not members of the officiating staff.
As noted, the skin form is merely a physician note stating a skin assessment has been observed on said participant. However, officials have the right per the rule book to overrule a skin form upon a physical assessment of skin during the weigh-ins, without appeal when determining the eligibility of a wrestler. The main idea you are missing is that this is a contagious skin disease. The role of the official is to complete a thorough skin assessment as their goal is the promotion of health and safety of all wrestlers, not just your wrestler.
Unfortunately, I completely disagree regarding "child endangerment." It sounds like it was more of a "child endangerment risk" to those who could have come in contact with the skin issue. And medical malpractice... I disagree there too. The officials have the right to deny a skin form upon a physical skin assessment. The bottom line is they are the last line of defense to again, promote health and safety of all wrestlers.