Instead of using the show message activity, you can create a page in the modeler that has the popup layout. Then you can use the show page activity to show this page and to pass the object "ValidationProject". Then your popup page would have a dataview where you have a couple different options on how to display the text that you want to show.
The easiest way would to use the text widget and then you can add some styling in the style section of the widgets properties. But it sounds like you would want to only have certain words bold or underline and not the whole string of text, so you would have to use the format string widget to create dynamic html.
In your case, you would want to setup one parameter and create something along the lines of this.
Hope this helps!