Thanks. The plans for each of the MERGE statements are very similar. Here's what I suggest you do; pick one of the statements and work with it in a query window in a test environment. Ensure your statistics are up to date - some of the estimated row counts suggest they are not. Then run the query, capture the actual execution plan and post it here.
For fast, accurate and documented assistance in answering your questions, please read this article.
Understanding and using APPLY, (I) and (II) Paul White
Hidden RBAR: Triangular Joins / The "Numbers" or "Tally" Table: What it is and how it replaces a loop Jeff Moden