Also, one does well to remember that being in love doesn’t always also mean that you are are with a true love. People have a remarkable abilty to pull the wool over their own eyes.
True love can happen more than once in some people’s lives. The perfect 20 something couple might find true divorce in their 30s and then another true love each in their 40s.
Many of the “evidences” of true love posted in the OP can also be felt by anxious, compulsive, delusional, or naive people.
Can’t live with out them? A centered person could.
Would go so far as to give up very important things for their happiness? Can also be said of unhealthy relationships.
Instead of simply trying to define what love is, sometimes it’s easier to describe what it isn’t. Or what it does, what affects it has. Note what one source (of debatable origin) has to say about love:
*Love is patient, love is kind. It does not envy, it does not boast, it is not proud. It is not rude, it is not self-seeking, it is not easily angered, it keeps no record of wrongs. Love does not delight in injurious things but rejoices with what is true and good. It always protects, always trusts, always hopes, always perseveres.
Love never fails. *
As to knowing when you yourself truly are in love with someone, I would say it’s when you can calmly look at all their faults in full honesty, and decide that you can accept all those negatives because of the amazing positives you see in them. Unromantic? Not really. When the love is that deep, life itself is romantic.
(btw, romance doesn’t always mean swooning and breathlessness, though it should at times. Sometimes it’s the calm acceptance that life is beautiful.)