Regarding the initial distance being "10 meters":
Please note that I am suggesting a specific way of looking at technique training - that I am looking at the acquisition of skill sets and not the matching of a self-defense scenario considered to be in a one-on-one relationship with "reality" and a given tactical response thought to be appropriate and thereby be "realistic."
Thus, for me, the starting distance is not so important in technique training. It is more a matter of practical coincidences than anything else. Meaning, uke comes in from wherever circumstances had them come in from - maybe the knife went flying across the mat from the last rep, hence, uke may be a little further back from nage when they start to zero in on the thrust. Or, maybe the knife from the last rep was handed over to uke by nage, so the zeroing in process happens from a closer range. Etc. Regardless, there is a maai that is associated with these skill sets, and the acquiring of these skills sets can only begin once that maai has been generated. Hence, sometimes nage has to wait a bit longer for an uke that started zeroing in from further out in order for uke to generate the required maai, and sometimes nage has to start immediately for that to happen if uke already had the maai when they were first given the knife. Either way, you don't move till the maai is generated.
Additionally, as I said above, I'm very much against trying to learn skill sets that are deemed "real" under the ruse of determining "reality" beforehand by negating what skills sets a person might know nothing about because they were deemed not part of "reality." Thus, I am not overly concerned with how far out a given uke might start his/her zeroing in for the tsuki in dojo practice, since I'm only concerned with where/when the required maai is generated. Moreover, I am also not overly concerned with an uke that might start out from "10 meters" (understood as an exaggeration for the reasons of making a point) because reality can very much include such an attack. In fact, my knife defense situation as a civilian, in which I was able to perform the knife disarm number one, was pretty much an exact copy of the so-called "stupid Aikido" knife attack: the attacker from the usual distance trying to stick a knife through my gut. Again, the exit was on the other side of the attacker, and there was no space in the room to run around. And, believe it or not, but you can't tell an attacker that wants to stick a knife through you that he/she should stop because they are doing it wrong, or not as good as they could be doing it, that they are too far and should be closer before they attack, or that they are holding the knife too tight and should be holding it more loose, etc. Go figure.
Regarding clearing the line of attack:
I think if you watch the video at 2:07, 2:14, and 4:14, you can see that the line of attack is cleared to the outside. One should not be staying on the line of attack to perform these disarms. One moves forward with the standard irimi angle (i.e. "attacker in front of me, but I'm not in front of him"). Remember, however, one only has to clear the width of the blade initially and then the knife-arm shoulder according to whatever technique one is employing. The clearing of the line is thus minimal but present nonetheless.
Please allow me to comment on something I think might be a bit confusing: In my experience, while it may appear that disarm III is the more risky and/or the one that might clear the line the least, if one were to try these disarms, one would see that disarm III is the easiest to pull off successfully and safely out of the group.
In disarm three one clears the knife and the same side shoulder entirely. If one misses the wrist trap, the knife simply continues in the thrust and one is to the outside front back corner of the attacker. What one is trying to do in disarm III is not walk head-on toward the knife but rather to let it go by and then to pull the arm into one's chest. Once the knife is trapped on one's chest, nage enters to the tenchi nage omote angle of attack. Since that entering requires a turning of the hips, the trap becomes a disarm. As the disarm proceeds, the knife stays inside the trap. Because the trap has one's chest to the outside of the knife, as one enters, AT NO TIME is nage in front of the knife. Throughout the movement, nage's chest stays in the same contact relationship to the knife. Again, if folks try this disarm, try to learn them, he/she will see, it is the surest, safest, of the three.
What about a video of someone else doing what you are saying - just for the sake of understanding???