***Neither a teacher nor a native speaker.***
() means I'm not fully sure.
/ means either could possibly be used.
In those sentences then refersto the past.
What you felt then was true love.
What you felt some years ago was true love.
(That was one of many examples.)
The other then is some kind of conclusion.
If it was love then, then it is never too late.
This is a logical conclusion.
Than is a completely different word.
It's better to find the true love late than never.
Use than when you compare something.
I love you more than he does.
Finding the true love is more difficult than expected.
I hope you understood most of the facts I said.
If you have any further questions, just ask.
Student or Learner