You can't really sub squats, they are what they are. It has to be barbell work, if the gym has no power/squat rack then really you're in trouble. How could you load a heavy weight otherwise? Dumbbell squats are possible but pale in comparison, the next thing I'd suggest is hitting up lunges but again you'll have to really use dumbbells for heavy(ish) work.
Ez bars are for curls & tricep work, it won't be stable on your back.
For a deadlifting routine, deadlifts are the routine. Your workouts should be based a round bench press (do not sub barbell work with dumbbell if anyones says to do this then they have little intelligence) military press (no leg movement) squats & deaslift. As you're training 3 days a week I'd highly recommend these program's as your after strength, starting strength by Mark Rippetoe or this one over at builtfit http://www.builtfit.com/workouts/strength-and-powerlifting/builtfit-5x5-workout
If you focus on big multi jointed compounds you can cut the crap out
people think you need to do a million & one assistances, check out my log (the last few pages) I train for strength/power & have added a lot off mass. There's only 1 Olympic bar?
Look over YouTube for technique videos by Mark Rippetoe, so search Rippetoe squats/ Rippetoe military.
What games you working on? I'm loving mass effect 3's multiplayer