monoprice.com is a good source for inexpensive high quality tv wall mount brackets. you’ll also end up wanting to hide the cords in the wall soon enough.
I really love the variety of mounts they have. I’m not sure if that’s the case for a 55"/13kg screen, but they have some mounts that are made to go on just one stud. That’ll probably pull on the screw in a way that it’ll hold a bit better!