Can you fix torn home button ribbon cable w/o replacing actual button

That’s a yes and no answer…mostly no. Depending on the type of damage, some techs can and will work on Home Buttons. However they are very difficult to work on and that doesn’t guarantee a solid, long-term repair.

I would encourage you to add a well focussed picture of the flex (add it to your question) so that I can see the level of damage.

The other possibility, if the phone is in good condition and you have the original screen, would be to have the screen replaced by Apple; they will automatically change the button and pair it to the logic board.