I really want to understand these things, so please bear with me.
I'm specifically wondering about the Three Dharma Seals or Three Marks of Existence. I've noticed as a novice Buddhist what seems to be a disconnect here. I hear it said that suffering is a Mark of Existence along with impermanence and non-self. To me, it's like putting an orange with two apples. Please help me understand if I'm off base here. All-pervading impermanence and non-self are a bit like those Zen koans that appear nonsensical on the surface because their goal is to make you get over yourself... the whole human tendency of making everything fit nicely into little compartments. "I hope this moment lasts, he's just a bad person, I'm proud of my looks" that sort of thinking. They're Marks of Existence in that they're road signs pointing toward a more direct experience of reality.
It seems weird to me to say that suffering, which I thought was the result of attachment and wrong views, is somehow one of these road signs as well. Am I totally misunderstanding the point of a Dharma Seal / Mark of Existence?
I've read that nirvana (extinguishing of concepts) is an alternative to suffering in this list. It points to a quality of reality that we misapprehend. Like impermanence goes up to our grasping and says "nope!" then non-self goes up to our cherished egos and pulls the carpet out, nirvana too goes up to our tidy world of ideas, then snatches our kaleidoscope away so we can see clearly.
I feel like the idea that everything is suffering is like going up to someone enjoying a sunset and saying, "Well, this sucks because it'll end and the sun will blow up eventually. Also, you'll die." I may be misreading the attitude, but in some books it can sure seem this way! Whether I suffer or not isn't contingent on some quality of the sunset or life, but the presence of aversion, greed, and ignorance, right?
Suffering is undoubtedly a crucial part of the human condition, but it feels weird to one day meditate on how impermanence touches every part of my life and the universe, then to try to do the same with the suffering.
So my questions about this: What is the purpose of a Dharma Seal? Why is suffering listed with impermanence/non-self? Is there a belief out there beyond Thich Nhat Hanh's books that nirvana is a possible alternative in this worldview?
I would also like anybody's thoughts on meditating on suffering in general.
Thank you everyone for being so forbearing with my questions! I hope they're clearer than last time. I accept in advance any silly newbie ignorance this post shows

