Short answers, pulled from the story.
Manilal Mohandas Gandhi (the 28th of October 1892 - the 5th of April 1956) was the second son of Mahatma Gandhi and Kasturba Gandhi. He is known for editing the Gujarati-English weekly Indian Opinion in Durban, South Africa, for nearly four decades, and for being one of the initial 78 marchers on the 1930 Salt March.
Yes, Manilal Gandhi was one of the initial 78 marchers who accompanied Mahatma Gandhi on the 1930 Salt March. He was subsequently imprisoned for his participation.
Manilal Gandhi edited Indian Opinion from 1920 until his death in 1956, a span of approximately 36 years. He had begun assisting with the Gujarati-English weekly at Phoenix, Durban, in 1917, and by 1918 was doing most of the work himself.
Mahatma Gandhi opposed the match because Manilal was Hindu and Fatima Gool was Muslim, and he believed religious difference would create irreconcilable problems for any marriage and children. He wrote to Manilal in 1926 expressing this concern, using the image of two swords in one sheath.
Manilal Gandhi married Sushila, daughter of Nanabhai Mashruwala of Akola, Bombay State, in 1927. The match was arranged by their families, with Mahatma Gandhi himself seeking her hand for his son. They had three children: Sita (b. 1928), Arun (b. 1934), and Ela (b. 1940).
Manilal's children Arun and Ela became social and political activists. Arun Manilal Gandhi (1934-2023) continued activist work, as did Ela Gandhi Ramgobin (b. 1940). Sita's daughter, Uma D. Mesthrie, later published a biography of Manilal.