What's the Name of That Book??? discussion

This was the first book, I believe in a trilogy, that I'm not entirely sure what the genre is. I read this around 2-3ish years ago (so 2016, 2015), but I'm fairly certain the book was written before then. If it helps at all, I believe the second book had the word "Key" in the name, and the third book possibly had "Skeleton" in its name.

Something I should mention is that I believe this book contained like a sort of overall background where humanity had gone through some sort of dark age (or are in one) where it was once like how it is today, but now is lacking the same tools, resources, and knowledge that we have.

To give some details of the book to help look for it, I'm going to list the things I remember in order that I remember them, so there may be spoilers ahead.

Starting off the book was something about the young, female protagonist (whose name I want to say started off with an A), climbing up a tree with possibly their friend below, and they find like a dart stuck in the tree, and was sort of a relic. If I remember, it had a story like 'wherever the thrower wants it to go, it will always find it's way there.' But she finds this in the tree, and I'm not quite sure about this part, but it may have had some sort of a map in there that leads to the entire adventure that unfolds in the story.

The next part I remember is her having quarrels with the school that she went to in her small town. She didn't like it, if I recall correctly.

Next was potentially something about a pair of men who came to her town in search of the dart that she had found. Shortly after, I think, they abduct her and go away from the town to follow the map. Along the way, I believe one of the two men that had abducted our protagonist was treating her quite poorly, which led the other man in the pair to resent the first. This leads to the second man freeing protagonist, quarreling and maybe eventually killing the first man.
The girl (protagonist) befriends this second man, and they continue their adventure as a duo.

Somewhere along the line, they end up finding this like retreat with a place where they stop and eat, and the place had like a stable, garden, and a sort of monk man.

They continue on where they end up in the second man's town where he has a girlfriend who is wheelchair-bound. Protagonist didn't know it was a wheelchair though, describing it as something with two wheels that the girlfriend could sit in because she could not stand.

They move on from this town to the final part of their adventure, some sort of cave with water inside of it. Apparently whatever they were looking for was down where the water was leading to. One of them had a rope around them to swim down to find whatever was there while the other held the end of the rope to pull them back should the other get in trouble. This is as far as I can remember from the book.

The Farwalker’s Quest, The Timekeeper’s Moon, and The Skeleton's Knife by Joni Sensel?

Google search - site:www.amazon.com post-apocalyptic dart tree map

Kris wrote: "The Farwalker’s Quest, The Timekeeper’s Moon, and The Skeleton's Knife by Joni Sensel?

Google search - site:www.amazon.com post-apocal..."

This is exactly it! Thank you for your help!

Great. Glad you found your book series, Peté.