Two more suspects were arrested in November following a two-hour chase that ended in a violent confrontation.
The seventh suspect, Adolf Malo Rangga, 34, was also found on Sumba.
If the suspects are found guilty of murder, they could face the death penalty.
Mr Ellis's death was "no doubt an execution-style murder", according to a senior police officer in the Bali capital, Denpasar.
He was found with his wrists and feet tied, wrapped in plastic and dumped in a ditch in the rice field near Sedang Village.
Ida Bagus Putu Alit, who heads the district's forensic team, said Mr Ellis' throat had been slashed three times.
Detective Wisnu Wardana gave more detail, explaining "there was a deep wound to the neck that had almost completely cut the head".
Police allege Mr Ellis' wife confessed to ordering his murder because he cheated on her. "The motive is because his wife felt embittered with the victim," Badung police chief Komang Suartana told News Corp.
"Because of many things. She said that her husband is often cheating on her. We allege that she paid the executioners to kill her husband."
Police have reportedly handed a brief of evidence to prosecutors in which they claim she paid the hit-men 150 million rupiah.
Mr Ellis was born in the UK but his parents, Nancy and Bob, moved him and his three siblings to New Zealand when he was a child.
He was raised in South Auckland and later moved to Australia. He met Aini in 1986 and the couple married in 1989 and had two sons, John and Peter. Mr Ellis also has a son Kelvin and daughter Christina from a previous relationship.
At the time of his death, his children released a joint statement.
"Bob was a loving and devoted father, grandfather, brother, son and husband. His loss leaves a hole in the lives of everyone he touched.
"His work in business created jobs for thousands of Indonesians. He was a good and honourable man.
"His integrity, generosity and spirit is evidenced by the way the business community both expat and Indonesian have rallied to support us and show their respects."
- Daily Mail and agencies