I have run into this as well - Crystal seems a little confused about where the text box borders are. I suggest adding a small right indent to the text box (right click on the text box, select 'Format Object', select the 'Paragraph' tab, and enter small numbers (maybe .2 or so) into the Right text box. This should help with the right margin.
As for the bottom cut-off, there is no margin that you can add. Can you add a line break to the end of your text as it comes from the db? Or, you could try a formula field to add the line break:
{table_name.field_name} + chr(13) + chr(10)