The analyses of a text #5

The protagonist, Philip, who has a club-foot innately, stays at a boarding school.
He tells his friend, Luard that it is a keepsake from his mother when he broke his pen-holder.
Misses Watkin is his godmother.

Philip took the two pieces of the pen-holder and looked at them. He tried to restrain his sobs. He felt utterly miserable. And yet he could not tell why, for he knew quite well that he had bought the pen-holder during his last holidays at Blackstable for one and twopence. He did not know in the least what had made him invent that pathetic story, but he was quite as unhappy as though it had been true. The pious atmosphere of the vicarage and the religious tone of the school had made Philip's conscience very sensitive; he absorbed insensibly the feeling about him that the Tempter was ever on the watch to gain his immortal soul; and though he was not more truthful than most boys he never told a lie without suffering from remorse. When he thought over this incident he was very much distressed, and made up his mind that he must go to Luard and tell him that the story was an invention. Though he dreaded humiliation more than anything in the world, he hugged himself for two or three days at the thought of the agonising joy of humiliating himself to the Glory of God. But he never got any further. He satisfied his conscience by the more comfortable method of expressing his repentance only to the Almighty. But he could not understand why he should have been so genuinely affected by the story he was making up. The tears that flowed down his grubby cheeks were real tears. Then by some accident of association there occurred to him that scene when Emma had told him of his mother's death, and, though he could not speak for crying, he had insisted on going in to say good-bye to the Misses Watkin so that they might see his grief and pity him.
[Of Human Bondage by Somerset Maugham]
1. I'd like to know if what "some accident of association" means.
2. I'd like to know the blue "when" clause modifies "that scene."
3. And I'd like to know what "speak for crying" means.
Thank you in advance for your help.