Should I have done more for my Article 15 and was I treated unfairly?

So, I been out of the military for a year, so I'm not mad or worried about the situation anymore, but I want to know if laying back and taking the Art 15 was the right choice.

So, I received an Art 15 for disobeying a direct order. Now here is the situation, I have a thyroid disease that makes me gain weight and its hard for me to lose it. I pop 1% over the percentage for h/w. My ex 1SGT and commander knows this so they gave me a break and told me I can come back in "a week" for a redo, this was on a Wednesday. I go throughout my week trying my hardest to lost these pounds with no effect, when I get a phone call on Monday after at the end of the duty day. Its was the SEPT trainer and the 1SGT asking me to come in to do the h/w. I told them that I could come it but it will take a while because I was picking my kids up from daycare. When I got my kids I found out there was an injury, so I text the SEPT SGT and let him know it going to take a bit longer because this problem has to be documented. He communicates with 1SG for me and they tell me to come to the on post gym at 0500 to get weighted. Now I been working off sight for a year now, so I complete forgot about the amount of traffic there is at the front gate (yes, I did leave early so I could be early). So, I show up at 0503, yes I know late is late, but as I walk into the gym 1SG is not at the meeting location nor anywhere in the gym for that matter. So, I think he is running late because sometimes he does that, so I wait there till pt formation at 0600. I go to pt think he has to be here and he wasn't leading pt either, so I go to the SEPT sgt and ask him where 1SG was at and he is mad but concerned. He tells me that I blew it and I missed him, I know I was late but I parked in front of the gym doors (only one way in and out) at 0500 and walk inside at 0503, there is no way I walk past this man. So, the next day (1SGT was out all day) I come in to his office on time and chews me out and recommends me for an Art 15. The punishment was very lenient and I only got extra duty, I was extremely thankful for that. But, I still think I shouldn't of got that because it was the first time I got in trouble at that unit the 2yrs I was there and being that at the time I was an outsource soldier for the NSA. I work 12hr shifts with the extra pt time I had to complete and the extra duty, I only had 3 hours of sleep before I had to do it all over again.

Also, the Art 15 paperwork it said I purposely miss two meetings with the 1SGT, one I had no idea about on Friday and the one on Monday. When I ask the 1SGT about it he told me that I said I would come back at the end of the week, not a week. Friday was my day off that week and nobody call me to come in nor told me I had to do it that day, I was in the o-room for a least an 2 hours talking to a friend.