Hello!
This is an RPG Maker game, they seldom have mouse interactions unless they were made in the MV version, which this game wasn't. Due to the fact that the game employs a hotbar script, it is very unlikely that it will ever have mouse support as the two scripts will conflict.
The [X] key plays the same roll as the [ESC] key, I will update this in the opening controls tutorial. But yeah, the [ESC] key would have worked for deleting letters as well... though [X} is generally the default in RPG Maker games.
The Gold Counter is a work in progress at the moment, it's a default that came with the 3rd party script, I plan to change it's appearance and display when I tackle the UI again.
At the moment there is no descriptor for the status effects. I'll try to add one in the near future.