Ok, well, it seems you're trying to educate yourself. Reading, etc, that's good. You're getting a good amount of protein for your bodyweight, and you're taking flax seed oil which means you've got balls ('cause that stuff is AWFUL! I can't even get it close to my mouth) :).
Here's the story...if you want to gain bodyweight and strength, you need to squat and deadlift. Those things add slabs of muscle onto your frame, all over, not just on the legs. Best builders of all exercises. Can I see your leg workout, please?
Also, you might think about dropping the reps down to the 5-8 range. Check out writings of Christian Thibaudeau, and esp. Chad Waterbury's "Set/Rep Bible" article.
Finally, while variety is good, and you have plenty of variety with your chest routine, variety isn't everything. Drop the machine/cable work completely, it doesn't help add strength and can be setting you up for problems down the road. Stick to 3-5 exercises per session/workout that hit the most muscle groups. My top ten in that I use are,in no particular order:
and military press (11)
And, let's see your back routine too.
Finally, as you say you are in a plateau, try a couple things: 1--cut off the "dead weight" exercises (ie-isolation/machine ex.), and 2--think about taking a couple easy weeks to recoup. Sometimes the problem isn't too little work, it's too much. Usually though, just cutting away the fancy stuff and going back to hard core basics works great (thanks Dan John!).