I think another important aspect of Luthen's view of himself, especially his own mortality, is the specific "I'm condemned to use the tools of my enemy," bit. He starts his monologue to Lonni with how he's given up any measure of kindness, love, kinship in his own life, the good, peaceful things that might've brought him comfort even in a galaxy ruled by the Empire, but finishes it talking about how he's burning his decency for the benefit of others, how there will be no reward, no gratitude for everything he's done in his pursuit of rebellion. But the "tools of my enemy" line sticks out hard for me, especially in the context of what he's planning in the scene.
There's absolutely a parallel to be drawn between Luthen and Dedra, as well as the ISB as a whole, with the way they each balance lives on ledgers of risks and benefits. Lonni is explicitly trying to offer Luthen a win, a chance to save a rebel cell from falling into an ambush, and Luthen remorselessly rejects it, because saving that one cell would mean burning the advantage Lonnie offers him and he refuses to give that up.
Sure, his monologue ends with talking about how his is "the ego that started this fight," framing it as him being denied a reward he's rightfully owed, and I do think that's definitely part of what drives his bitterness, but I believe the greater part is just that he despises what he's become even as he recognizes its necessity. The role he plays in the nascent rebellion, balancing who knows how many disconnected cells and movements across the galaxy, before it grows enough to get the capital R in its name is undeniably a critical one, but it's a cruel, vicious role, and Luthen sees himself as a monster who's only redeemed by setting himself against greater ones.
Make no mistake, he's absolutely aware that he could die at any time, whether through betrayal, a cunning trap, or a simple slip-up, which also informs the inevitability he views his death with. But I think that even if his plans all go exactly as he hopes, if the Empire falls and a new Republic rises from its ashes, he wouldn't be able to find a place for himself within it. Not because there wouldn't be one, not because no one would glorify, justify everything he's done, but simply because he himself couldn't stand what he became to get there. Neither him nor the ghosts in his dreams.