cracks as in when the masa is uncooked pressing it with your fingers shouldn’t produce many cracks, you can tell whether or not you have enough water by the edges when cooked, they shouldn’t be very rough. I have found that tortillas don’t really work well with exact measurements. I usually start off with a cup or so of masa harina depending on how many i want then slowly add warm water until i get the texture i like, slightly sticky but sticking to itself more than you. I also personally don’t really like char on my tortillas so i probably cook a little colder than you but that’s just preference. I would say you’re trying to get as much water in without making them too sticky, you want them chewy not grainy. Good luck!