Tex is not conceived to manage paragraphed footnote. Reledmac use an hack, which is very sensitive to geometry. As explained on § 19.1.6 of the handbook, you may have to redefine.
In you case, i get something correct with footfudgefiddle
Note that your header doesn't fill the space reserved for it. Nor does the text reach the top of the text area. (The first baseline is \topskip below the top.)
Please see that an exact solution depends on how you define 1 Inch in cm or mm. I simply use here the fixed version for
1 Inch = 25.4 mm.
Be aware of rounding errors for the conversion of Inch to mm ...
Because you gave no mwe (please next time add one!) I can only guess what you are doing.
Please see the following MWE containing the "formula" to get ...
You can tell LaTeX to place an extra wide image into a box that is the size of \textwidth with a \makebox. It will be centered in the box and spill out to the left and right.
You can use fill space there is no need to calculate the space between boxes. Also it is almost always best to leave a blank line before \vspace.
The small gap at the bottom is de to the fact that the frame drawn is leaving for the usual case of text on the last line so there is for descenders such as y and g . If you want the bottom of the last box to ...