the last paragraph of the novel, is Okonkwo’s final act understood by the District Commissioner - has it made a difference in the fight against the white man?

Okonkwo's death makes no difference to the white men, If anything, it emboldens their sense of power further the Igbo further.
No one in the clan can touch the body. Suicide is a crime against the earth goddess, and so the body must be handled by outsiders. Obierika says bitterly to the DC that Okonkwo was one of the greatest men of Umuofia. Because of the white man, he has been driven to suicide and will be buried like an animal.
The DC is quite curious about Igbo customs. Okonkwo's death may make a lively paragraph in the book he plans to write about the British victory over the savages of Africa. He has already chosen a title: The Pacification of the Primitive Tribes of the Lower Niger.