First of all: I think it is already pretty awesome and quite usable - it already works quite intuitively (several ways to interact) and just needs a bit of finetuning.
To answer the specific question to make visual distinction between paragraphs:
1. more space between the buttons and the next paragraph.
2. a line between the buttons and the next paragraph
3. highlight the active paragraph and the corresponding buttons (on hover or selected field)
Most of those effects don't need much to work, they can be subtle, just a slightly different shade.
One more thing you could do is use the statistics to help grouping, for example by placing them under the buttons, still right aligned. It will serve as a natural separator.
I think those need to be clearly separated in style from the buttons and the text to indicate it is meta-data.
Some more feedback on the page itself: I would make the buttons just a bit more distinct from the normal text: at this moment it is all the same font, colour and size, and that gives the impression that the (unused) buttons are part of the normal text flow.
You could break this up by using a different font (serif vs sans serif), displaying it in italics, using a different font size, using a different color and background color.
There's a balance to be found: it needs to be distinct enough to not confuse it in the overal flow, and yet not so distinct as to completely seperate itself.
I would also display the dropdown menu on arrow down, and move the items in the dropdown menu a bit closer together. Perhaps indicate the dropdown functionality with a small light-grew arrow on the right side of the field that has focus to make it more discoverable.