First off, thank you a lot for your critique, I'm glad you enjoy the game and made it this far :) We are aware that the game is partly very challenging, which is on purpose, but I acknowledge that parts of the experience can get frustrating. You are almost at the end, so it would be a shame if you wouldn't make it through, therefore from here on out:
______SPOILERS_AND_SOLUTION_____
The map in the diary only pictures the area the raft is in, with the black parts being isles and landmasses. The goal is to get the raft trough most of the level without it breaking.
You can light the tree on the right of the raft's spawnpoint by lighting the minecart and pushing it into it(just like in the mines). The lever for the mine-rails is to the right of it. after that you can progress with the raft to the right where the tree was, where you can access the saveroom from another side again and save, and then progress upwards with the raft.
I hope you will make it with these hints and in any case we are very excited for your gameplay video :)