CSS for separating lines in stack gallery title?

Hello all,

I'm trying to figure out what will allow me to create separate lines in stack gallery titles. In my first screenshot (111) you can see the name of the artist and the title of the work keep wrapping onto one line after I save. I want them on two different lines like in my second screenshot (110). Using the Mojave template. 

Also looking to change to the size and family for the title but can't get it to work--this is the css I use for a different page, even with adjustments for stack I can't get the format to work with the stack gallery:

.image-slide-title {
font-family: arial!important;
font-size: 18px!important;
color: black;
}

Any advice for either issue??

All help is much appreciated!