1. The scale difference is most likely due to non applied transforms.
You should always make sure that your library node has applied rotation, scale and location. You can do that by pressing crtl + a
You'll have to re-export it afterwards of course.
2. You should create a folder called library inside your track folder and inside that library folder you should have a folder named like your library node (in this case "stklib_tower_a").
Your main object also has to be named correctly, (put "_main" at the end the rest should be the name of your library node export folder) as well as the folder that contains your library blend, it should be the same as your export folder.
You should always make sure that your library node has applied rotation, scale and location. You can do that by pressing crtl + a
You'll have to re-export it afterwards of course.
2. You should create a folder called library inside your track folder and inside that library folder you should have a folder named like your library node (in this case "stklib_tower_a").
Your main object also has to be named correctly, (put "_main" at the end the rest should be the name of your library node export folder) as well as the folder that contains your library blend, it should be the same as your export folder.