OK, this I didn't realize. So after you lost control, you said you saw it going full speed, and now we know it was not going straight.it was not travelling straight, that is the problem. Let me visit the farming fields again. Lets see.
In the replay of your flight route, at 14:50 it appears you are making a beeline home in one direction headed due south, when all of the sudden the flight record goes wacko. Presumably, when the flight record went wacko is when you lost control. If you saw the craft during this time when you lost control, almost home, which direction to you recall it heading by LOS? From minute 14:50 to the 12% mark at 19min, the average reported speed calculates to about 2600m distance, if you believe the telemetry data. It is possible the telemetry data is also totally wacko too, but it's all you got. And, if you witnessed the craft going multiple directions after losing control, this make things really difficult to estimate.
Good luck with the search.