[Andrew Green]

Javascript is certainly not my strong suit, but here is a solution:

<script>
    var currcount = 1;
    function add_stats()
    {
 	   var temp = new Array()
		for(c=1;c<currcount;c++){
			temp[c] = document.getElementById("stats" + c).value;
		}
        if(currcount>13) return false;
        div = document.getElementById('inputs');
        current_html = div.innerHTML;
        div.innerHTML = current_html +
'<select id="stats'+ currcount +'" name="stats['+ currcount +'][option]" onChange="check_value(\''+ currcount +'\')">'
    +'<option value="magicfind">Magic Find</option>'
    +'<option value="pointbonus_general">Pointbonus General</option>'
    +'<option value="pointbonus_char">Pointbonus Characters</option>'
    +'<option value="pointbonus_thread">Pointbonus per New Thread</option>'
    +'<option value="pointbonus_reply">Pointbonus per Reply</option>'
    +'<option value="strength">Strength</option>'
    +'<option value="dexteriety">Dexteriety</option>'
    +'<option value="vitality">Vitality</option>'
    +'<option value="energy">Energy</option>'
    +'<option value="usertitle_color">Usertitle Color</option>'
    +'<option value="usertitle_glow">Usertitle Glow</option>'
    +'<option value="usertitle_style">Usertitle Style</option>'
    +'<option value="ads">No Ads</option>'
+'</select>'
+'<input type="text" size="23" name="stats['+ currcount +'][value]" />'
+'<br />';

		for(c=1;c<currcount;c++){
			document.getElementById("stats" + c).value = temp[c];
		}
      currcount++;
    }


</script>

You'll have to do basically the same thing for the other field. For the second problem you could go with a "onChange" call off the select box, to call a function to check if it is one of the defaults, if it is fill it in.