Hi Freedom.
Great job in studying form and doing your best to lift properly. Lower back issues could arise for structural imbalances (where some muscles are working harder in some areas than they should in an effort to compensate for other muscles that just aren't engaged or ready for a specific lift/movement) For example, the core muscles of the trunk help to support the lower back during all of the compound lifts. If the core is not strong enough or if it begins to relax during your session then there will be unnecessary stress upon the back.
Just a thought.
Now, to correct this: First thing I would do is hire a trainer at least for just one session to check your form. Someone who has a good eye and who is familiar with the lifts/exercises you are doing. Make sure that one part of your body is not compensating in some way for a lack of strength to complete the movement successfully.
Second, keep in mind that in almost all cases with the free weights the following will be true:
Keep abs engaged
Shoulders squared
Squatting/deadlifting relies upon great hip mobility and the end of the movement relies upon you driving through the heels not through the front of the foot. Also...and this is a big one these movements are initiated in the hips. You sit the hips back. This sounds easy enough but really takes time to learn to do correctly. I suggest a lot of glute activation, and hip opening exercises. If the trainer you work isn't familiar with glute activation exercises before you do a squat or deadlift then find another one.
It's that important.
If you continue to experience back pain, like real back pain then please have it examined by a physician. You probably should anyway. It may be that there are structural issues beyond just improper lifting technique. Especially if your lower back pain wraps around the hip and or to the front of the knee.
I also want to add that you may think about adding core exercises to your workout beyond crunches. Often times these can aggravate an already painful lower back.
Add in planks:
http://www.youtube.com/watch?v=iaA1r5w4CSk
Bird Dogs:
http://www.youtube.com/watch?v=qzffg0V9xhk
pallof presses:
http://www.youtube.com/watch?v=zGOP0...=24&playnext=2
stability ball rollouts:
http://www.youtube.com/watch?v=Gg4o7...=30&playnext=8
By all means though, get some assistance from a trainer to check form and from a physician if you are experiencing "bad pain" and not just muscle soreness.