Your UI likely should not have a hover interaction or a tooltip for a display this large. It would be benefited by using a click interaction and a modal with scrolling and search. This would allow you to offer all your shortcuts in a non-overwhelming way. I have set up a web demo of a possible implementation of that concept but it uses some modern code and may not run in all browsers (I have tested on latest chrome and edge versions).
The important things to note from the demo are the spacing: which allows easy scanning of the text, the hover effect: which keeps focus to the line at the expected place, and the differentiation between monospace and non-monospace font: which also allows for easier reading.
Many places do this but the best example I can think of is the Atom code editor. They offer a complete search of the keyboard shortcuts and their UI allows for easy scanning. This makes for a pleasant experience for the user.
Please let me know if you need a gif of the functionality in case you aren't able to access the webpage.