First of all, I wasn't expecting that much detail. I'm sure there are better things you could be doing with your time. So know that I REALLY appreciate this and it helps a ton.
I'll try and clarify some things, but I can already see some gaps you've pointed out that need to be filled. I want to be clear that I'm not hand-waving your feedback here. Each point you've made is already on the drawing board and ready to be used in a restructuring of some scenes (no major overhauls or anything, but adding details where it feels necessary). The goal is to basically communicate the intention behind the dialogue.
When it comes to Oswyn, he's currently a Lieutenant, which is a lower rank than Captain. The key difference being that he's not yet in command of his own company/group of soldiers. The rank/position of Captain is currently vacant, and was being primed for Oswyn. It was really just a matter of him wanting to accept the rank and proceed with the formalities to make it official. As shown in the cemetery scene, he's having doubts about the direction he's going because Ziedrick was known as a hero who was known for his victories in battle. Oswyn believes that Emperor Junon's pursuit of peace means he probably isn't going to have any opportunities to come close to measuring up to Ziedrick, so he's having his doubts? This is where Elynor's advice about honoring Ziedrick in different ways changes his perspective and motivates him to step up and help with the investigation of the stolen Dagger when that opportunity presents itself.
As for the reason for letting Angus go, I thought it was pretty clear that Angus used his leverage to reveal who had the Dagger stolen. He did give Angus his word that he'd let him go, and so my goal was to also use that decision to convey to the player that Oswyn tries to be an honorable man despite being somewhat conflicted at times.
You're spot on with Ysabel, and she will become a regular character at some point in the game.
Your concerns with Bayard are also spot on, and that's where I see the largest gap. I actually don't mention the specific Guild that he leads outside of his status menu profile, and that's a huge issue. I'll be sure to add some context there through dialogue in a future update. With regards to his association with Oswyn, Emperor Junon does say to Bayard during the meeting in the throne room: "Bayard, I assume you have no qualms about working with an old friend?" I'm not sure if that's enough to drive the point home. But I figured that, along with how candid Bayard and Oswyn are with one another, would be enough to convey to the player that they grew up together. Again, the scene can probably use some work to be more to be either explicit or even implicit in more ways.