How can I find verses with two or more occurrences of the same word? If I use the AND command I get all the single occurrences, many of them counted twice!

You can use the <FOLLOWED BY> command. For example, there are 40 verses and 43 occurrences of Nathan in the Bible. A search for “Nathan <FOLLOWED BY> Nathan” finds the three verses where the name occurs twice, giving a total of six hits.

An even better way is to use the Construct window, putting the same word in two or more columns with a WITHIN between the first and last to permit intervening words. This allows you to search, for as many repeated occurrences of the word as you want.