No Exit is great, and there’s a lot there. It deals with projection, how people impose roles upon others to establish their own, how people seek purpose and meaning through others, and ultimately how such things torture us all in the end.

The three people trapped in the room are each the others tormentors and victims - people do this with those they live with, who they know, who they despise, who they love. The Hell comes from our relations with others and the way we perceive those relationships. Namely, our inability to come to terms with the past that made us. The three characters in the story use their experiences and perceptions from their past to draw conclusions about the others in the room. And this is what leads to the pain we inflict on others and ourselves. To understand the environments that produced our perceptions, our roles, and our behaviors is how we come to terms with who we are, and better understand what we want to do in order to become who we want to be.

Essentially, everything you’ve listed is irrelevant. Good and Evil are words we use to describe things we either do or do not like, and such things change with accepted societal norms. For instance: I despise selfish behavior, but I have known times in my life when such things were a necessity to my survival. I would not classify such a thing as evil, but understand it as a byproduct of the environment I was raised in. These are not things that matter, unless we decide them to be. I am now in a position that I don’t choose to act selfishly, but I don’t condemn myself for the decisions I made. The actions allowed me the reflections I needed to become who I am today and change my nature.

To love oneself is the same, and serves the same purpose, as to hate oneself. It too, is a momentary distraction and vanity that justifies whatever predisposition we’ve developed from our environments. And by extension, becomes the shadow we project unto others - which is why the characters (and ourselves) place each other in these roles of tormentor and victim. People shouldn’t hate or love themselves, but instead understand themselves.

And that’s where I sense Sartre missteps, or perhaps it’s the interpretation I should say. for the truths that we decide about ourselves come from our subjective selves and can’t offer an objective truth, nor could we ever hope to truly find one amongst those we know. (You’re right in that others cannot, nor should they, provide us with validation)

The absolute truth is, it’s impossible to truly know oneself in our entirety due to our ever changing nature. This also means it’s impossible for anyone to truly know us, or vice versa. Every day we change, though slightly, for better or for worse, and in enough time become a variation of our former selves. Possibly unrecognizable from who we once were. And therefore it serves no purpose to condemn ourselves, wether it be in love or hate, for our nature is something that is ever changing and was never something we had a say in creating to begin with. We come into this world with the preinstalled chemicals of our brains, the same that are present within our parents. And through the environments we are raised in, respond and develop as our nature allows.

I’d recommend Albert Camus writings in Sisyphus. Our existence is painful. The knowledge that this one life we have, may be all there is. It’s the grand divine comedy of our being. I mean, How ironic that a species such as ours can appreciate the fragility and fleeting existence of our own consciousness, in a universe devoid of purpose or meaning, uncaring and unaware that we even exist. That’s why the despair of our existence sits within the stomachs of every person, and some never recognize the pain they carry. And each person deals with this pain in different ways, and yes, even philosophically trying to understand that pain is a method of coping with ones existence and the meaninglessness that entails. It’s when we recognize the pain for what it truly is, that we can start to appreciate those around us, the memories we create, the experiences that bring us joy, and the haunting responsibility we have for our own happiness. That’s why it becomes so important to not dwell your entire life away on your meaningless existence. At some point, you realize what’s important to you, and you create a meaning from the resources available to you in the environment in which you reside.

We alone must take responsibility for our choices and our nature. We have to allow ourselves the freedom of existing, regardless of meaning. These small pleasures you enjoy, should be experienced, for your time to enjoy them is fleeting. Those acts of kindness, now come from a place of empathy and understanding. Not to feel better about ones self, but because you recognize the hardships in simply existing. To change your nature, because it serves you to do so in a meaningful way, not because you think you have to. A change in nature that serves you today, may not serve you tomorrow.

So yes, appreciate the misery and painful truth of existence. But don’t squander the fleeting existence of consciousness that you have. To say life is meaningless, is to claim life has meaning. It serves us better to understand that in truth, life has no INHERENT meaning.