Yeah I've made them a few times before and each time I try adding more water, but still get the crackly surface, I think maybe my pan is not hot enough.
Yeah, in researching recipes, they're about 50/50 for and against adding fat. The hardliners say never to add fat as it's unnecessary, but others say add some lard or butter to increase the pliability. The ones I made are still fairly pliable, they have a crackly surface but don't actually crack or tear when folded.
I grew up with home made tortillas and my mom would probably disinherit me if I added lard or something like that lol. So I'm very much in the camp of only salt, water, maseca and nothing else, but I think experimenting is always fun so that is up to you.
I would try making them a bit thicker, and like you said a warmer pan. Also, flip them sooner and then flip them back at the end if you want them to be toastier, that may help too.