Before becoming a minister Addison worked as a tutor. He helped young men prepare for their education. Between his work and his need to visit his wife he had no way to advance himself.
He turned his thoughts to the Colonial Church and sought to go and minister there. We are not sure if his wife passed away and he left his two surviving children with an aunt. OR if he travelled with the aunt and his children while his wife remained behind pregnant with their last child. The details are a bit fuzzy.
He had great plans for his time in Upper Canada. By the time he passed away he realized some of them. The work was hard. He had a circuit of 150 miles to cover, people minister to, battles to work around and so forth.
He said "My Mission, is very laborious; I must either neglect my duty, or make a circuit several times in the year of more than 150 miles through a wild country;" and he adds, that he had performed his duty "with humble and conscientious assiduity, and had struggled with very narrow circumstances." (source)
He enjoyed his work among the Indians, baptizing several of them.
He ended up on house arrest after the War of 1812. He made regular Chaplain type service to different divisions of the army. Continued to minister to the Indians. He was a hard working man, who allowed his house to be a place of refuge. He was the longest serving missionary (serving for 40 years) and when he died, his death was regretted by all. His hand was active in the start up of many churches, and in the conversion of many Indians.
Early Canadian Missionaries.
Rev. Addison on Niagara.
Dictionary of Canadian Biography.