I’m not sure I understand the second question – you can only have one link per marker, although you can have two markers for the same location.
For the first question: you could try adding posts_per_page=-1 to retrieve all of the posts that match. Also, you can test some queries by just entering them in the blog’s URL, for example:
http://myblog.com?post_type=initiative
Have you checked the documentation on this as well? There are some examples:
http://mappresspro.com/mappress-documentation