Quote Originally Posted by David75
Why does Sanae-san tell Ushio to go to the Toilets to cry!
That's purely insane! I won't talk too much about it and the psychology behind that, but to me it shows that Sanae has a severe problem too and I even wonder if she's somehow responsible for Nagisa's condition... (I'm maybe going a bit far here...)

Regarding Tomoya, we now understand that unconsiously he choosed Nagisa because he felt she was so weak she could die on him. I wonder how unconscious it was, still he lived that to the extent he ends up in almost the same situation his father was around his age.
Yes, Sanae has Munchausen by Proxy Syndrome, and loved that her daughter was sick all the time and is now dead.

Sanae told Ushio to go to toilets to cry probably because she didn't want Ushio to look like a crybaby like Nagisa did. Especially in front of her father. That's why the other stipulation was that Ushio could only cry in her own father's arms, because after that point, he would have accepted her. The point of this roundabout method, I don't know, but Sanae probably knows best. Perhaps Tomoya would have recognized his daughter's plight sooner if he always saw her crying, or perhaps he would have only seen more of Nagisa in her and labeled her more of a burden. The same may be for Sanae. Having another crybaby would remind her of her own deceased daughter. Crying only in the bathroom also gives Ushio the outer appearance of being happy, instead how lonely she has felt until now.

Regarding Tomoya, you've got the cause and effect backward. After Nagisa died, Tomoya kept thinking that everything would have been better off if he had never met Nagisa. He wouldn't feel hurt, beaten down and depressed. He wouldn't have a constant reminder of his dead wife in Ushio (he had asked Sanae whether she was alone or not when she dropped by, referring to her usually bringing Ushio along). Tomoya remembered that Nagisa, though she was weak, had little tricks to give her just enough confidence to continue on. He chose her because he, being the weaker of the two ultimately, was relying so much on her. When everything clicked, he finally figured it out and realized that he was even weaker than his own "deadbeat" father. In her own crybaby way, Nagisa supported Tomoya and his rehabilitation. When he lost her, he went back to the way he was before he met Nagisa. He cries at the end because having finally realizing what he's become, all the memories of how Nagisa supported him flood back, and he relates those to his daughter on the ride back.

In short, when she died, Tomoya forgot why he loved Nagisa. He forgot how she was strong, and could only remember where she was weak. He chose Nagisa for her strengths, but mourned her for her weaknesses.

EDIT: I think this post covers your newest one as well David.