Regarding your question—What does it mean: "We are all originally Krsna conscious entities."—We are always with Krsna. Where is not Krsna present? So how you can say that we were before? You are always with Krsna and when we forget this fact we are far, far away from Him. In the Isopanisad it is clearly stated that tad dure tad vantike "He is very away, but He is very near as well." (Iso. mantra 5). So this forgetfulness is our falldown. It can take place at any moment, and we can counteract this forgetfulness immediately rising to the platform of Krsna consciousness.
Yes, your have correctly answered your second question by the purport that Arjuna's mind was already absorbed in knowing Krsna as his friend so he should not give up that status but he should only change his vision for the time in order to see the Universal Form of the Lord.
Regarding the three beads missing from your set of japa beads, just string three beads in place. That is all that is necessary.