There is no automatic way to equally spread those items I'm afraid. Even if you used a table you would be stuck with the same number of entries in each row.
If you need them exact that you will need to wrap each pair of radio and inputs in an element that is floated left and each float given an individual width that makes them all fit.
You must have a full valid doctype for IE to work or you are making it behave much like iE5 and lose all the goodness of the last 10 years.
Also note that is not valid to wrap a span around block items such as the form element in question. Spans can only wrap other spans or other inline elements.