Eh it was his fault. He could having taken time to woo Ruka but he caused this big mess
True... teen Taiga has a shitty attitude but so thus teen Yuka: he was trying to avoid Kaoro because he is a nerd and only get back at him thinking he was also an Omega.
They did not truely understand what was happening to them, that is why in the school rooftop scene it was only Taiga and Kaoro who was excited, for Taiga's part I think it was enhanced since they were fated also when he asked his other friends about Yuka's scent and it smelt sweeter on him, Kaoro's was supresing his rut.
Taiga also saw how Yuka bonded with Kaoro and that they were childhold friends. Maybe he knew he was wrong, he also mentioned how Omegas are born to be empregnated by Alpha's, this is what made Yuka avoid him and his gang in the first place even trying suicide, he knew Yuka doesn't feel safe around him or out of concience for what he did to him, he gave way for his fated to be happy to someone who will not treat him like a baby machine.
The old Taiga was very understanding even to that other Omega, so yes maybe he was a coolkid on his teens but it doesn't mean he can't care or empathize.
It was sweet of him to make his fated feel secure even if it was not in his arms.
What? He didn't know they were fated till much later. He was a shit head who thought he could do whatever because he was an alpha. Going as far to want to gang rape his friend. He couldn't do anything after Yuka was bonded that's why he did nothing. It's not like he was even in love with Yuka and Yuka wouldn't have even wanted him. He was never in love with Yuka, he was just obsessed like others with the idea of a fated partner.
Taiga knows way back. Remember after the incident another Omega was in heat in the school but he felt it was not the same sweet scent than Yuka's and when he asked his friends if it were the same scent they smell from Yuka and said 'yes', he then realized that it was only him who smelt that sweet scent.
He then remembered the heresays that fated pairs has unique and sweeter scent then random Omegas.
He distance himself to his fated because he knows Yuka's and Kaoru's bond and thinks they really love each other.
Remember in middle school he reprimanded his friends who wants to hang out again with Yuka after the incident? He knows they were at wrong.
He knew they were fated but he never gave chase to Yuka. Its kinda sad and heartbreaking to see him gave way to make his fated happy. ┗( T﹏T )┛