How can I rotate part of a caption?

[SillyFreak]

Rotate elements are block level, so you’d put it in a box to have it as part of a line. See here for a longer description/discussion on block and inline elements:

How can I align to images side by side?

Images (and most other elements, e.g. paragraphs, headings, tables, as well as shapes like lines and rectangles) are block level, that means that they are laid out vertically under each other. The opposite is inline. There are a few ways to arrange block content horizontally. Here, I would suggest a grid. Grids put multiple things into cells, and you can of course have a grid with only one row. Since you have multiple images, a grid with two column will do the job. Related is the table, but …