I think it's a relic from when you converted the topmost subform from positioned to flowed. You don't need that subform any more. You need to do two things:
1. Delete the (untitled subform)(page 1) subform. Highlight it in the hierarchy, right-click and select "unwrap subform" from the menu.
2. You'll see that your remaining content moves up to overlay the header. This is because you were using a 1" margin at the top of the subform to space the content below the heading. This is not the best way to do this. The master page has a content area (the magenta dashed rectangle) that defines where each page's content will be layed out. The items on each page will get placed starting at the top of where the content area is defined, then layed out in order down the page according to the order in the hierarchy. When a page's content flows below the bottom of the content area, a new page is added and layout continues at the top of the next page, again at the location defined by the content area. To accomodate headers/footers, you adjust the placement of the content area on the master page so that it starts below the bottom of the header and ends above any footer that you might have.
In your case, click on the (untitled Content Area) on the hierarchy. The display should show the master page and the content area will be selected. Drag the top of the content area down so that it begins below the header. That will fix the overlay. If you want a larger bottom spacing on your document, you would drag the lower part of the content area up, creating a larger bottom margin.
Hope that explanation is clear. I will take that raise since you're offering...