Use a table with fixed cell dimensions instead of a text box.

Since you are making a template, another suggestion (for item 1 of your
post) is to use a Text Form Field (Forms Toolbar). It does allow for
specifying the number of characters allowed as well as other Property
adjustments. A Table cell can be constrained to prevent it from expanding,
but does nothing to prevent the user from typing as much content as they
wish - its just that anything beyond the size of the cell doesn't display.
I've found this to be problematic on occasion. The Text Form Field can be
inserted into a sized table cell if you wish, in order to visually indicate
the extent of the space allowed.

As for #2, Word doesn't offer 'picture boxes' in the first place, so what
you are asking cannot be done. The image 'containers' are created only when
the the graphic is inserted. Your best bet is to create a table cell or
rectangle autoshape to act as a placeholder for where the image should be
placed, but the images should be sized in a graphics app *before* being
inserted into the doc. Resizing images in a word processing program
(especially increasing the print dimensions) can drastically deteriorate the
image quality.