Is there any evidence that Takeshi really wanted to committ suicide?

Well, if you want to know, he did attempt(and failed to attempt) suicide. It's in the chapter Yamamoto Takeshi of Katekyo Hitman Reborn. The reason behind this is because of over exertion of his arm and he strained it and thinking he won't be able to play baseball anymore, he went to the rooftop of the school and attempted to kill himself by falling, only to be saved by a half-naked Tsuna who got shot by a dying will bullet.
It's found in one of the first 7 chapters. Hope that helps :) I'm a fan of Yamamoto Takeshi.

DUDE!!!!!!!!!!!!!!!
spolier man that's just such a spolier i can not believe that :(

The only evidence you get is because he's on the edge of the roof and he says he's going to jump but it feels like he changes his mind afterward... it's like in chapter 3 in the first book

Yes.The story were like this:The next day at school, Tsuna hears that Yamamoto is jumping off the building since he broke his arm during practice and thinks that it’s his fault. As the whole class goes to Yamamoto’s side, Tsuna hides from him. Reborn then arrives and uses his Dying Will Bullet on Tsuna who runs and is seen by Yamamoto. Tsuna tries to reason with Yamamoto, saying that he was arrogant and that he is sorry. Tsuna then runs off again but Yamamoto is able to grab him causing him to slip and the two falls down the building. Reborn shoots Tsuna with his bullet and Tsuna is reborn in midair with the dying will to save Yamamoto. After Tsuna grabs Yamamoto, Reborn shoots another bullet to Tsuna’s hair whorl which causes his hair to grow and be used as a spring. The other students then leave thinking that it was only a joke by Yamamoto and insults Tsuna of being a pervert. However, Yamamoto thanks Tsuna and Tsuna is able to gain a close friend. However, Reborn thinks of it differently and thinks that Tsuna has acquired another family member.