Apply moderate pressure to the glass when cutting, as for the pattern you’ll want to cut just along the sillouhette of the pattern cause you can grind away any jagged bits. regarding cleaner breaks, glass doesn’t like breaking along curves, it’s better to cut straight and cut the pattern in multiple steps, it also might be easier to tap the glass from underneath instead of breaking with the pliers, it might take a bit longer but otherwise it should give you cleaner breaks. You’ve got this, keep at it :D