Aim offset look at mouse location

I’ve created an aim offset for my character in a top down click to move game. The aim offset works great. the variable goes from 0 (look to the right) and 100 (look to the right) I just want the character to look at the mouse location. I tried getting into some math where based on the mouse location I can calculate the Tangent angle and get the angle that the head should look but it breaks apart once the character moves from the origin point.
Is there a better way to get this to work? It seems like I need to some how transpose the vector of the mouse location around the characters rotation. I’ll attach what I tried and an image of the game to give you and idea of what I’m trying to do.
Thanks in advance for any input!

Thanks this helped me get the rest of the way there. For anyone looking at this in the future this is how I did it