If I understand correctly, you want a Views block such that, when I am on the "Node Q" page, the view traverses the relationships all the way up to Pathway "Node X", and then down again to "Relation 1", "Relation 2", and "Relation 3".
Start with a Contextual Filter "Content: ID", configured with a default value to get the Content ID from the URL. This will provide the view with "Node Q" as a starting point.
Next, we need to add a chain of relationships, each one dependent on the last.
- Add a Relationship "Content using [Endpoint B field]". This connects "Node Q" to "Relation 1". I suggest setting the relationship's administrative title to something more precise, like "Relation from node".
- Add a Relationship "Content referenced from [Endpoint A field]", configured to use the previous "Relation from node" relationship. This connects "Relation 1" to "Pathway X". Again, set a better administrative title, like "Pathway from relation".
- Add a Relationship "Content using [Endpoint A field]", configured to use the previous "Pathway from relation" relationship. This connects "Pathway X" to all the Relations referencing it in Endpoint A. Set an adminstrative title like "Relations from pathway".
This should get you there. When configuring your View's fields, make sure to use the "Relations from pathway" relationship.