Just to be sure, so you changed it, right? So it’s:
//#define US902 ///< Used in USA, Canada and South America
#define EU863 ///< Used in Europe
Also, I don’t know how easily the Arduino IDE detects changes in libraries; you may want to do some full compilation.
Not related to your problems:
I’ve no idea. For outdoor gateways you’ll always have line of sight from the sky. (Though the antenna orientation might not be optimal?) Beware that the range might be quite far then, and that you’re using a radio spectrum shared with others. Many others when transmitting from a high location.
Also, with SF12 you cannot send every 5 seconds (or every 6 seconds, given the 1 second delay for the LED): even when doing the experiment for only an hour, a 2 bytes application payload only allows for 25 messages on SF12 on the TTN Fair Access Policy, and only one message every 2 minutes for the maximum duty cycle regulations. LMIC will enforce the latter but not the former. TinyLoRa does not enforce anything. Finally, a hardcoded SF11 or SF12 is not allowed. (But I assume it’s just an experiment, not something you’d be using on a regular basis?)
For the very same reasons: while testing your code from home, if SF12 works, I’d surely go down to try better data rates if possible.
Also, TinyLoRa always transmits at maximum power; I don’t know what that maximum is, and if it’s within EU limits. All said, when using TinyLoRa then one’s own code needs to ensure one plays nice in the shared radio network.