Before you delete the photos from the iPhone, disable iCloud Photos on the iPhone.
Now you can delete all photos from the iPhone that you do not want to keep on the iPhone.
On your Mac disable "Optimise Mac Storage" for Photos and wait for all photos to download to your Mac.
Now you will have two options:
- Either you stop using iCloud Photos at all and just import the new photos from your iPhone using a USB connection.
- Or create a new, empty Photos Library and make this library your iCloud Photos Library. Befor e you switch from your current library to a new library, you have to be sure, that all photos have been downloaded from iCloud to this library.
- For the new library use "Optimise Storage". Now you can delete the photos, that will download from iCloud to this library to erase your iCloud Photos Library. Empty the Recently Deleted album, whenever. you have more than 1000 photos in tis album, so it will not get too full.
- Once you have a new empty iCloud Library, you can use this library for syncing photos between the iPhone and the Mac. Whenever you download new photos and videos from your iPhone to this library, move them to your larger main library to archive them. Then you can erase them from the smaller iCloud library or or just keep your favourites there.
To move photos between libraries use "File > Export > Export unmodified Original" and then import the items to the other library. Or get yourself the full, paid version of PowerPhotos. It can move complete albums between libraries.
To work with more than one Photos Library see these Help pages:
