The default MS bibliography styles don't have this problem because they are not using a table layout. Try adding more than 100 sources to a bibliography and you will see that sources are no longer correctly aligned for those styles. A table layout is the only way to guarantee that this problem doesn't occur.
When you have finished your Word document, convert your bibliography to static text. Then set the column widths of the table columns to fixed sizes. The pdf generator should honor fixed sizes.
When you have finished your Word document, convert your bibliography to static text. Then set the column widths of the table columns to fixed sizes. The pdf generator should honor fixed sizes.