1 I think you can't, if you find it's possible then let me know! lol
2 what you put in the option code is sorrunded by double-quotes so to use a variable you can just put this
$setting[value] instead if you want to use a function then you will have to close the string in this way
PHP Code:
<b>test</b>: ".explode('-', $setting[value])."continue writing html
and if you want to use if condition or more advanced code it's more complicated