i think a lot of this depends on, well, both of you. i pretty much loathe 'role play,' i.e., pretending something. This is all very real for me, so from my perspective, the first step is to discover what really may touch you in this area, and to discover what really touches him.
Preface/disclaimer: i know this is just my take, not intending to make this a universal application.
Right up front, to me the term "worthless bitch" feels contradictory to me. If he wants you to make him feel like a bitch, it obviously has 'worth' to him? And i think that is key... for both of you. If you get that, suddenly this leaves the field of play and becomes real. There is something in and about him that needs and wants, that is a "bitch," it isn't pretend or play. i believe understanding that can empower you, but in my book, the power is only there if it is something you 'really' want/need. To me, the real power here is not in making him feel like a bitch, but in exposing, surfacing, that he is one.
i think the "worthless" part comes from his embarrassment over his femininity. So embarrassed that he has to macho it up by referring to it in derogatory terms "worthless bitch." The truth is, he has a feminine part in him that is starving. The 'worthless,' imo is really embarrassment over being something/somone he is not supposed to be.
Off the cuff, i can think of all sorts of ways you may be able to surface this in him, but again, the real power imo would be finding ways to surface the 'bitch' that also touch something in you... the deeper the better.
You could arrange an appointment for him at a spa to get a Brazilian Wax and leave a package for the person doing the wax to give him after, maybe a Victoria Secret bag, with a pair of lace panties for him to wear after the wax.
Another approach, especially if he is not well endowed, is to use terms to minimize his penis. Never refer to it as a "cock" or "dick" or typical manly terms. Maybe once it's waxed, comment on how you never realized how small it is, but that is tricky. Again, i don't believe in pretend, so it would have to be something you really perceive or believe. Maybe get him a micro cage from Amazon (they're relatively cheap) and they internalize the penis and make it look more like a 'clit.' Restrict access to his penis, control it and surface that he really needs to get his pleasure from being penetrated, that he's really not a penetrator.
A few thoughts.