My race was hot and miserable!

I wan't LAST, which I am happy about. This race had me questioning everything: WHY did I think I could do this, WHY did I think a July race would be a good idea, WHY did I "think" I can run with all of these "real" runners, WHAT am I doing wrong with my training, I CAN'T do this....and so on for 6.2 miles! This was my 2nd race ever, with the first one being the Royal Family 5k, so I knew it would be "different" than Disney.
90% of the people on the run were actually running ALL of it! I never saw anyone who looked like they were doing intervals, though there were a handful who did walk from time to time. I started off with running for 4 mins, since EVERYONE was running and there was no way I could stop to walk that early without being run over. From there, I did my 1:1 and did ok, for a bit. In hindsight, I probably should have done my gel before the 1/2 way mark, but I was worried about how it would affect me. In the end, I did two and I am not sure either one of them really did anything. I never felt "better" or "stronger" and on the way back in and I had to drop my intervals down to running for 30-45 seconds and walking for a minute. At mile one, my time was 11 mins

(I'm not that fast) but later I looked at my watch and I was figuring I had dropped to 15 mins average. It was at that point, I was slowing down since I wasn't going to get a time to submit. All I wanted to do was finish it! I crossed the finish line at 1:20:45 I think. It wasn't a chip race, so I don't know which time they will use. (the picture my DH snapped shows 1:20:45 and a second timer on the ground with 1:21:44. I know I started about a minute-thirty after the first people crossed the start) I'm too new to races to know for sure what it end up being. The official results are posted yet.
I still don't know what to do about my training. I felt like I had never run that distance before and I would just die! I actually ran the same trail and more last weekend and still struggled on the way back, dropping down to shorter runs, BUT I was running at 7:00am and ran 7.89 miles. I don't know if the heat was the issue or if I am doing something wrong. I'm just worried that 10 miles will kill me now.
One important thing I learned: Caffeine gels will NOT work for me! I was mentally and physically exhausted when I got done and really wanted to go to bed. I tossed and turned all night and it took forever for me to fall asleep! While this could be good for the ToT after party (me being awake), I don't want to miss the next day at the parks, so I will need to figure out what fuel will work and which one does not have caffeine.
2nd thing I learned from the race: warm, almost hot water is cruel to offer at the end of the race! Two guys were like, "here, take some water. Take two and pour one over your head, it will help." I took a swig as I continued past them and almost choked! It was hotter than the water I had been carrying on my belt!
So there is my race summary. I "think" my time will help me move up in the corrals, but am not sure. Any thoughts or advice from the experts? I welcome it!! I'm "off" today, but tomorrow I get to dive back into training.