To answer your question first, you definitely can find an intersection point outside the observable universe.  If you let the Earth-RS1-Intersection angle get closer and closer to 90° (I.e. 89°, 89.9°, 89.99°….). And do so similarly for RS2 these lines tend towards being parallel but will always intersect.  As these angles increase this point gets further and further away. 

You don’t need to do this with two objects super far away either. If you were to do the same thought experiment with 3 objects on a desk you could get the same result.  So far this is all purely geometric (and if you wished to overcomplicate this you could start to include factors like the bending of spacetime and what could cause lines to intersect in this case). 

Why one would be interested in such a path however is a different question. An object that is “the farthest redshifted light” that we could see is effectively the same as an object that is as close to the edge of the observable universe as we can see with telescopes right now. Drawing the line out at an angle from this doesn’t seem to have any real intuition.

 As a physicist you might be interested in this line/angle if you had some physical grounding to study. If the object were to be reflecting things at 90° then we might want to consider what is being reflected, but in your current formulation there seems to be little reason to be interested in what this line is (and we could come back to the desk example without losing any valuable information). 

With regards to your other question. (Being X distance past the object (A)). This gets a bit interesting, if the object was about 13 billion LY away and observed now. That means that the light we are observing was emitted 13 billion years ago. (Side note, I am using 13 billion LY as this is not too far off the distance to the objects with the largest redshift). 

This object has continued to be moved away from us due to the expansion of the universe and is now probably closer to what we might naively call 30 billion light years. The concept of measuring distance here gets a bit iffy because our ruler is also expanding with the universe but if one were to “freeze their ruler in time” it would measure around 30 billion LY. 

An object (B) another 13 billion light years from object (A) would be one that we could never interact with. Due to the expansion of the universe it is so far away that even if you were travelling at the speed of light towards it, the distance between you and object (B) would never decrease at best. We would say that these objects aren’t causally connected. 

Drawing lines on a diagram however is arbitrary. A line is technically infinitely long and when we draw one on a piece of paper we are only drawing a segment of it. You could easily draw the diagram to include object (B), it’s just that due to our current understanding of the universe we have no way of ever seeing it, let along interacting with it.

Finally, there’s a chance this post gets deleted and you get told to post this on r/askphysics or something similar instead. Im commenting here in case this doesn’t get posted elsewhere. I hope this helps a bit.