Hi bread201,
welcome to this Apple (user-to-user) Community.
Re: iPhone storage: "iCloud Photos: Is there anyway to delete all the unnecessary photos, and stop sharing them? "
Seems if you stop the sharing (from an unknown person?), the photos will disappear too.
Apple Support have an article online (link below) that may be helpful:
See: Manage Photos sharing settings on Apple devices - Apple Support
or
If the photos are being "shared with you" (eg: via the Messages app):
See: Manage Shared with You settings on Apple devices - Apple Support
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If needed: More info. / Support / Contact options etc.:
There is a "Get Support" link (online chat, phone, eMail etc) at the bottom of the support website (link below):
Website: iCloud - Official Apple Support
All the best :-)