How much history do you have with the company and would you lose a steady stream of income if you were deactivated as a shopper? I will not shop anything for $3 - MSC’s offering these rates are completely unrealistic in my opinion (and their emails go straight to the trash folder). I have avoided phone shops altogether because even the ones that pay $15 appear to require too much time for the compensation offered.
I think I would email the help desk first and explain the situation if I were in your shoes (include the fact that you are not comfortable and that you might easily be identified) instead of just canceling the shops. If the person receiving your email is helpful, maybe they can cancel the shops for you with less penalty than if you just drop a ton of shops via the website. If not, maybe they could provide an alternate solution that would help make the shops easier for you. If this isn’t the case, I would complete the shops since the commitment has been made, reminding myself the entire time that I would never accept a shop like this again

Good luck!