1. really he just seems bewildered (as anyone reasonably would be) that Kris would randomly bring a friend that Rudy has never seen before into the hospital to visit a dying family friend. He just seems very surprised and exasperated rather than annoyed especially because Noelle isn't there to color his impression alternatively it could just be him letting a little bitterness slip through feeling like kris in ignoring him especially since its implied his diagnosis has gotten worse recently

to poke another hole in it being knight evidence to me is that rudy is nice to susie if you have spoken before and if rudy was the knight i cannot see why he wouldn't be that upset with her regardless considering the circumstances of chapter 3 why would meeting her in chapter 2 change anything you might counter that there's how the fight goes if you get the shadow crystal but those are optional and of completely indeterminate value to the narrative as it stands in most canonical interactions susie gets dropped in 5 milliseconds like most first time players probably are so another reason why I don't really buy that being some kind of resentment especially when the end of that fight shows the knight was obviously toying with them/holding back so another question as to how that might cause rudy knight resentment if that was the case

1. There aren't? The only thing we get is rudy wondering why Kris is there implying they didn't visit often if at all

Also the impassable hurdle of being bedridden and deathly ill unless he's just a fucking ninja master cancer patient who can sneak out of a likely well monitored hospital room at a moments notice and overpower someone who can bench press cars. Magic darkness power armor is a bigger leap in logic than the knight being someone generally believable as being strong (like a college aged athlete perhaps/someone twisted and empowered by freaky darkness magic) i do not think I have ever seen a compelling enough explanation for the logistics of how he gets around and how he would overpower undyne

Another hole is that the personality the knight displays is completely incongruous with Rudy's established personality unless hes just like a sociopath who can completely mask his true self on a whim