We're currently working on a HTTP based API for a future Pi-hole v6.0, see
https://github.com/pi-hole/FTL/pull/659
This API already includes the features you're requesting:
1 is available with POST and DELETE to the API, 2 is implemented with GET requests to the same endpoints.
The paths will be
http://pi.hole/admin/api/dns/whitelist/exact
http://pi.hole/admin/api/dns/whitelist/regex
http://pi.hole/admin/api/dns/blacklist/exact
http://pi.hole/admin/api/dns/blacklist/regex