This is no good at all:
move_and_slide.floor_max_angle = 1.55555
It's a function, you have to call it with its parameters in parentheses.
Plus, you must pass it a velocity, or you won't move at all anyway.
The doc lists the parameters and they must be used in order:
move_and_slide ( Vector2 linear_velocity, Vector2 floor_normal=Vector2( 0, 0 ), float slope_stop_min_velocity=5, int max_bounces=4, float floor_max_angle=0.785398 )
So you would call it for example, like this:
move_and_slide(Vector2(100, 0), Vector2(0, -1), 5, 4, deg2rad(30))