Might want to check w/ support but I don't think you can delete just a few points like that yet. 


Last time I did this it was a while ago, they had me delete that map which you already did. Make sure the auto sort by boundary setting is turned on in the Org settings. Then make a boundary around the home place so that extra crap was inside it. Plus the good field had a boundary of course. Then when you reprocess the file(s) for that field on the files page it will look at the boundaries and split it up. You can then delete the "whole" map of your shop field since it's not separate from the good one.