For future users, here's the answer I received from a ShareThis Support Agent (http://support.sharethis.com/customer/portal/questions/862200-proper-share-type-for-st-twitter-hcount-and-st-fblike-hcount-dynamic-specification-through-js-#sthash.F82qZiuZ.dpbs):
You are getting malformed buttons because you are using an incorrect "service" name. You cannot use service names like these - "st_twitter_hcount"
Please use service names as - "twitter","facebook" and then you can specify the button type in "type" as "hcount" or "vcount".
Below is an example on how to achieve this using the code that you have implemented.
shareServices : ['twitter', 'facebook', 'linkedin', 'googleplus', 'email', 'reddit', 'st_twitter', 'st_fblike','st_wordpress','st_linkedin']
shareType = ( shareService.match(/^st_/) ) ? 'hcount' : 'chicklet' ;
if( shareService.match(/^st_/) )
{
shareService=shareService.substring(3);
};