What you might want to do instead is have a popover with a portal of questions to select from, or a popup window with a list view that you use as a selector, rather than a drop down. This way you can have complete control of the display.
means: You can not really controll the width of dropdown fields )-:
could be another feature request - dealing with popovers will patch, not solve (-:
Thanks Mike and Markus,
I can't use a popover with a portal because the layout itself is a portal and popover from a record in a portal can't have a further portal. I know, there is a hack for this problem, but I wouldn't use it. I tried another test: I added a calculated field to the question-table which holds only the first 150 characters of the string, so the combo-list is small. It's not a good "hack" but it will work.
I have sent in a feature request (under product ideas)