The diff lock will usually unlock by itself after it is no longer needed, since steering right or left gives it the slack it needs to disengage. To unlock it manually use left or right brake for a moment.
You don't need to keep pressing the pedal after it dropped, indicating that the dogs aligned and it engaged.
That video in the high brush was all poison ivy, I felt terrible because my middle daughter ended up with a massive case of it on her legs. The 13 acres is literally solid ivy and a real pain in the butt!!
It's going to work the tractor pretty hard. I would do it myself, for a limited once-a-year project like a vegetable garden. For earning a living working long hours I would get the (smaller) appropriate size.looking to rent a 4' tiller but the smallest anyone has is 5'.... Is that too big for the 186D