Can I attach the top plate of a 135' wall to the metal suspended ceiling grid Or what do I need to do to attach it to make it not so flimsy since its such a long span?

The ceiling grid is not going to help all that much. not on that long a wall. How far above the ceiling is the roof and is there something there that a brace could be attached to? A V brace every so often or do the wall in sections with a longer stud between each section that extended to the roof structure.