Concerning your question about everything in the picture being straight, use some photo editing tool on your computer to first make sure that the horizon/garage floor is dead level, then see if there's a tool that overlays a grid across your photo. You could just draw in your own horizontal lines if it can't do that for you.

I'm with engfineer on loosening up the little horseshoe clamp deal bolts to make wiggling easier.

 

Got a rubber mallet handy? Start smacking the crap out of it. (Last resort)

Like the others say, loosen the endlink nut so it is right at the end of the thread and then try to put the other side on again.

Otherwise, mallet attack!