You're not the first to come across this issue and it crops up several times in the "Ideas" section of the Tableau Community site. Unfortunately Tableau currently does not allow you to resize the title of a horizontal drop down filter or parameter. Your best bet is to hide that title and replace it with a new text box, which can then be resized. Put both the text box and the drop down into a horizontal container to keep them together tidily.
This post covers the solution too: size of quick filter title not changing ??
Hope this helps.
Have you tried increase the height of each parameter, it seems there is space for height.
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Use the first line of the parameter as a title or to give direction to the user and then hide the title. In your calculated field set the value of this parameter line to NULL or ' ' depending on the data type.