If you do not want the diversity of creatures I would stop adding any food. As the diversity of food disapears the diversity of creatures should too. Less creatures should be still around when the material is mostly vermicastings.

Can you tip over the bin into a second bin so that instead of everything being on top, the new critters will be buried? Some might vanish.

~ equinox "add cardboard" equinox

I think I'd prepare contents for another bin ... freeze kitchen scraps. Get a supply of animal manure or homemade manure. Then OUTDOORS tip out the infested bin. Sort worms out into temporary holding place[in peat moss or compost or ?]. Wash out infested bin [I'd wipe with diluted bleach] rinse and let air and dry. Then start all over again with new bedding, new food and rescued worms. That sounds a little extreme, sometimes draconian measures are needed to recover from a mistake [scrap bin outside with holes]... with the alternative being to give bin away. BTW ... you've probably read enough posts on this forum to realize that many experienced verm-keepers have killed their first one or even more bins.
BTW ... just noticed another set of articles on RWC .. scroll down to "Worm Bin Mites" & "Fruit Flies & Fungus Gnats"
http://www.redwormcomposting.com/popular-vermicomposting-topics/

Here is a link that might be useful: Homemade manure

Excellent info, just the advice I needed. Thank you!