tightened the chain today

[grego]

hi all

well this was my first adventure turning a wrench on the bike. the chain had about 1 1/4 inches of play.
i adjusted the chain to just a tad over a 1/2 inch. while cleaning the chain and sprockets i noticed these cracks on the rear hub. they look like just surface cracks, but being a newbie i don't know weather to be concerned or not.. another thing i noticed is that there is about 1/4 inch of movement of the rear wheel if you keep the sprocket still. is that normal ??

i found this liquid wrench chain lube. it says its safe for chains with o rings as you can see by the pics. has any body else used this and if so what is your opinion verses what you used previously ??

all help and comments greatly appreciated by this newbie

ride safe

grego