Caret Browsing

Microsoft Edge and Mozilla Firefox support a mode known as caret navigation. Beyond the tab and shift-tab stuff mentioned earlier, Safari doesn't have a specific mode for that, and it—like most other apps on macOS—uses the system-wide assistive support. See macOS keyboard accessibility for information on enabling and using keyboard navigation, and also see the mouse keys support. Those settings will work across most apps, including Safari.

Here's a list of the Safari shortcuts...

If I'm understanding you correctly, Open Preferences in Safari and turn on This option:

Try using "Command + Up and Down" arrows for full page scrolling and "Option + Up and Down" arrows for partial page scrolling.