The military father theory is interesting, as MH has several qualities that line up with former military and/or military brat. (This doesn't mean I think it is the gospel, but it makes sense for the theory)
His posture stands out a little, to me. There are certain ways he is standing and faces he makes that remind me of military members I knew (I am sure everyone rolls their eyes hearing it, but I was in the Army for over 10 years. I only mention it to add a little credibility to my claim)
He was reportedly doing the hike without GPS, and only using maps. I didn't see the mention of a compass, but any seasoned soldier will always emphasize the importance of having map and compass readily available, checking it frequently to ensure you haven't gone off your intended path, and if you have, readjusting from there. This makes me think that he was taught or learned navigational skills at some point. (A counter agreement could be that if he stuck to the beaten path, it would not be too overly difficult to stay on his intended direction).
A (perhaps unimportant) observation regarding military familiarity is that MH is ALWAYS wearing some kind of headgear. I do not think I have ever seen a picture where he was not wearing his Columbia hat or blue beanie/bandana.
MH also fits the physical description for a military member (and potential vet). He was white, he was between five feet 6 inches tall and five feet 10 inches tall, he was approximately between 150-180 pounds (when healthy). This physical description matches (probably under guessing) 60% of the U.S. Army Ranger Regiment. It is also my physical description.
Could be a brat, but unlikely a vet
Things that contradict MH once being a military member are the lack of tattoos and lack of tobacco product usage (that we know of with perfect teeth). However, I personally have zero tattoos, and I have never had to wear braces. I had one very small cavity, one time, over 10 years ago and I was devastated. I have a very small filling that is not noticeable. I have never used tobacco products, ever.
A big thing that stands out to me to rule him out as a vet is his pack. I have looked at multiple pictures of him wearing it, and it is almost as big as he is. Sure, military members can carry large amounts in their rucksacks/ALICE/MOLLIE etc. The point is, it looked like he had absolutely no idea how to pack his items for maximum space and weight efficiency (on the flip side, I have met soldiers who were in the military for many years and had just as bad packs, one of which was a SSG who had a lawn chair hanging off his pack, with several other items swinging from it
)
Fingerprints is another big one that is mentioned to rule out former military. However, as I stated before, if anyone was going to misfile, lose, forget, accidently throw away, save under the entirely wrong folder, it would be government and military record keeping systems.
Abusive Father
I touched on it before, but I don't 100% buy it. This information was being relayed from interpretation, which can be different from person to person.
One of my favorite stories to tell is how my highly religious father was so upset with me, he took his glasses off and balled his fists up. He turned red, and pounded his head with one of his fists. He leaned forward and challenged me to hit him, saying something to the effect of "COME ON, GIVE ME ONE GOOD REASON, COME ON!!! TRY TO HIT ME!!!" (Much like the account about MH, this all happened in our front yard) Some people hear this story and immediately feel deep empathy for me, as if I was traumatized. I was not traumatized at all, and personally I find the entire set of events to be hilarious. In my mind, when this happened, I was thinking to myself "Hell no, I am not going to try to hit him, this dude is mad as hell"