Sensei has literally begged for Help before. He can "show weakness" (and has been for a few updates). He just wasn't willing to,
for Ami. He's too selfish to put her needs above his own.
Not wanting to look weak, pathetic, and incompetent, which he is, even with Ami's welfare on the line, is
still selfishness. Hence needing Niki to spell it out for him, before he'd quit being stubborn.
Sensei knows far more than that. He has literal examples of better parents than him, which he brings up, like Chika and Kaori. (Plus there's also Sara, Maki, and hell, Tsuneyo is probably doing a better job with Noodles, their son.) He also should have a form of Google. A 5 year old could have tried harder than him. (And that's me being generous since I've known a few 3 year olds that knew how to look up stuff on their phones.)
Key Fragments: