Shove a wedge between the chain and the bottom of your bar before you sharpen. It keeps the tooth upright and tight against the bar.
All my saws above 50cc are square grind. I can tell you a few things about that. First, if you are cutting mostly hardwoods I would forget the square grind. It is super fast for cutting pines, spruces, and firs, but not so hot for hardwoods. Second, if you are someone who like to steer their cut, you can't with a square grind. How you start the cut is how it is going to end, no tweaking as you go. Third, if you are having trouble filing round I would skip the square grind. It is a whole new ball game and takes precise and patient work with excellent light. Fourth, if you are attempting a plunge cut with a square grind be ready for some serious kickback until you get the hang of it. It is five time more likely to do that than the round grind chains. Also, square grind dulls faster. If you hit a piece of metal, you had better have the patience of a saint.
I deal with mostly aspen, spruce and balsam, the square grind shines with those. If I was cutting maples, oaks, or similar wood I would not have them on my saws.