regarding connecting nodes in sequence ordered by datetime, I dont see where there is a date time value in your MERGE.
But also I have had the same concern for example loading similar to these posts here at community.neo4j.com into Neo4j where a single post might have N number of replies and wanting to build out a sequence for example
(n:Post {id1}) --> (n:Reply {id:1}) --> (n:Reply {id:2}) --> (n:Reply {id:3}) --> (n:Reply {id:4})
but choose not to build out a N relationship path but rather simply had
(n:Post {id:1}) --> (n:Reply {id:1})
(n:Post {id:1}) --> (n:Reply {id:2})
(n:Post {id:1}) --> (n:Reply {id:3})
(n:Post {id:1}) --> (n:Reply {id:4})
and then ran cypher and used match (n:Post {id:1})-[]-(n2:Reply) order by n2.datetime so as to get the order