ADHD could be an issue. When I was a kid, we called that “being a kid” but today they drug everyone up. Talk to an AME about this. There is a possibility you were misdiagnosed but you’ll have to prove it.
DA at KTVL was about 8400'. I would not take a 140 up there in those conditions. One person has pretty serious head injuries... probably no shoulder harnesses as they were not standard on the older 140/180s. My 1968 180 has them, but I am not sure if they are original.
I have flown near it on an IFR flight plan when they allowed me through the restricted areas but I was still probably 20 miles from the runway there. Lots of other places to land.
I give my IR students a clearance to copy starting on about the 3rd or 4th flight. True, it’s not a “real” clearance, but we do fly it, and they get used to copying it down. By the time they get a real one, it is no big deal.
Are you a US citizen? Do you have legal residence in the EU?
When I lived in the Czech Republic (on a residence visa as I am American), I was unable to fly on a US license even in an N-registered plane. I was told this was because I was a legal resident of Europe. To get a Czech license I was...
Make sure you can get a medical certificate. You you have been on any ADHD medication, be careful. Hopefully at 15, you have had no encounters with the justice system either.