(sorry for my bad english)
I'm also having the same problem in my TextBox. I also do not know how to use the "Auto Font Size". Ok, it automatically changes the font size according to the layout, but how to set the size of my font? I want my font-size at 30px but when I use "Auto Font Size" it becomes very small, like 10px. My solution was to Resize it every Tick or whatever. Like this:
-Set TextBox size to (300*LayoutScale, 40*LayoutScale) (My TextBox initaially have 300px,40px)
-Set TextBox CSS Style "Font-size" to ""&30*LayoutScale &"px"
The "set size" worked fine, but the "CSS Style" don't. Nothing happens (with Auto Font Size off). All looks right to me, but I don't know why it doesn't work. Does CSS Style doesn't accept this ""&30*LayoutScale &"px" expression?
I searched for my problem, and I found this post.
If anyone has any solution, I will be very grateful!