ok i know that you may not like destiel, but i promise you, as a fellow sam stan, the second half, especially the last couple chapters, of to become a man goes fucking wild for sam. it drives me feral even to this day. no spoilers tho.
when i was reading this fic, i would refer to to exist again because the interconnectivity is off the charts. the dialogue from the two fics are the same but the perspectives are different, so reading to exist again only or to become a man only is completely different experience off what is basically the same series. its like how arrested development's orginal formatting final season had all the different perspectives and jokes set up in each episode that didnt make sense until you watched the entire thing. and it is hilarious. the setup, which seem offhanded and weird pieces of dialogue in to exist again become key plot elements in to become a man. and deans perspective of magic is so different from sam's and cas. you just get a really good feel for how much of a freak sam is and how normal dean is in a world full of magic. it just adds another layer to world building.
and the fic addresses all of the issues i have about dean. it doesnt just wave a wand and make him unproblematic, but demenior makes dean work for it. he has character arc. he is not perfect at the end, but he is trying and that is what is important. and you also gotta to read to become a man just because of the whole cliff hanger for to exist again. once the to become a man has caught up with to exist again. i mean. the answers are definitely worth the wait.
i can tell you what specific chapters that are important for sam. i never reread the fic in its entirety but only to specific chapters that drive me, as a sam stan, insane. but its also the little moments between the major sam plot points that treat sam and deans relationship with such care and fucked-up-ness that i would recommend that you dont. you got to find the parts that drive you insane yourself
oh my god. i almost forgot about dem's characterization of purgatory. i dont want to spoil it, but it really expands on the wrongness of the leviathans and purgatory that supernatural never was able too.
and overarching themes. the overarching themes. its fucking beautiful and ties up everything so well. sam and dean have their own themes and arcs (which you can pretty much get from their story titles) that complement each other so well with the overarching message (the love it takes). it is wild. no it is well thought and planned.
warning: there is eldritch monster sex scenes in to become a man. you can skip it if you are not into it. there are warnings at the top of those chapters.
i could write essays about to exist again and to become a man. i could talk about them all day.
and it was such a joy reading it in real time. the theories and analyses that the readers made comment section for each chapter. the real time interactions with the author. it just made the experience so much better. and the music. oh the music that goes with this fic.
if i were you, i would reread to exist again whenever the timeline matches up with to become a man. it so worth it.
and the dem shares many of your cas/angel headcannons that are fully fleshed out in this fic.
oh and @demenior has little fics of the love it takes on their tumblr (this fic series is why i joined tumblr the first time around).