One thing about the disrespect factor - it's certainly believable about the Kauravas. If Dushashan could strip Draupadi, it'd definitely conceivable that he or one of his bros could have insulted Pandu as a kid. Similarly, what Duryodhan said about Kunti was not totally out of character.
However, one thing about the relative strengths of everyone here. It's well known that the Kauravas were very mediocre warriors, if you take out the legends - Bheeshma, Drona, Ashwatthama, Bhurishrava and so on. Duryodhan, for instance, lost every challenge he ever had in front of him. He failed to capture Drupada. In the battlefield, he was easily defeated not just by Yudisthir, but by Drishtadyumna as well. So it's inconceivable that Nakul or Sahadev would have lost to him. His brothers were even weaker. The CVs have no idea about the reasons behind the Pandavas.
If Bheeshma, Drona, Ashwatthama & Karna had been out of the picture/neutral and had it been a battle just b/w Kauravas & Pandavas, Bhima alone would have crushed them. The reason Arjun was needed was all those others - Bheeshma, Drona, et al. As noted in the rangbhoomi thread, the rangbhoomi was an exhibition - where each prince could showcase his talents. If it was gonna be a battle, Duryodhan would have lost to Nakul himself. Remember, when the Pandavas accosted Duryodhan in a lake, Yudisthir offered him the option of choosing any of them to fight. He'd not have done that had Duryodhan been superior to any of them. Same was the case here.
Also, the rules of this contest seemed really convoluted. If Bhima could forfeit on the technicality of making Duryodhan bleed - something that Bheeshma came up w/, then how did Duryodhan not forfeit for attacking Yudisthir from behind? In other words, if Duryodhan won against Yudisthir, Bhima would have won against Duryodhan, and vice versa. There is no consistency of standards here.
Finally, in the precap for tomorrow, Karna & Arjun are shown fighting, and Arjun's arrows get dissipated by Karna's armor, which is when it becomes visible to Kunti. But in the original, Karna was denied a fight: it was after Karna was crowned that Adirath congratulated him, and the caste question saw to it that a fight didn't happen. That was why Karna became a lifelong friend - he wanted a battle w/ Arjun, which he got to have @ Draupadi's swayamvara, Matsya, and finally Kurukshetra. But had Karna gotten the opportunity that they're gonna show him get tomorrow, he'd have been pretty satisfied.
Also, Kunti saw his armor & earrings first thing when he appeared, and recognized him. It didn't become visible just b'cos Arjun's arrows failed to penetrate it.