Yes, I did go by the elevation of the closest airport. I'll be honest, I don't think filing one will help safety or other pilots in any way. I should have tried harder to get a Class B clearance, and when I could, just scrapped the video shoot for the guy, and tried it another time. I am kind of upset with myself that I didn't do that, but there is nothing I can do about that now, other than learn from my mistake. If there was any true mistake here, it was a lapse in judgement on my part. I understand what you are saying about the errors involved, not to mention, as I said above, this was not the congested area of the city I was flying over (by city, I just mean the borders of the city). It was right on the edge of a yellow area on a sectional, but it isn't "the congested area of a city" so reading the exact wording of 91.119, I would say I actually only needed to be 500' AGL. The city I was over has a huge mall with houses surrounding this mall, and I would call that the "congested area of a city" and straight line distance, I was close to 2 miles from this mall.
I guess I just wanted advise, and this place is great for that. I was tagged up on radar during the video, because I was talking to approach. Like I said, safety was in no way compromised. The only thing compromised was my judgement haha. Due to that, I don't think a NASA form would do anything, other than immunity for me, but at the same time, as you said, I may have actually been 1000'AGL due to errors, and the fact that I don't know the exact elevation there, plus the fact, by the wording of 91.119, I think I actually only had to be 500' AGL anyway.