He lives with his Indonesian mother in the east Java city of Surabaya but his family want to bring him to New Zealand where they believe he will receive better medical care.
Convinced the condition is a product of black magic, his mother Yuhanie Marisa Latinia is keeping her son in chains and has demanded $6 million as a "starting point" before she will consider releasing him.
Attempts by the family, New Zealand and Indonesian officials to retrieve Simon have so far failed.
Mr Donaldson said the family would keep the pressure on until a solution was found to bring Simon home.
His ex-wife's lawyer told him Ms Yuhanie had signed an agreement with the head of Indonesian immigration at Waru that said she would release Simon when he was better.
Considering his son's condition would most likely never improve, the agreement was meaningless and no different to anything his ex-wife had said over the last three years, he said.
Mr Donaldson also accused Ms Yuhanie of making threats against him on her Facebook page.
In one photo she is posing as if firing a gun and underneath the caption reads "I'm gonna get u DD!! Bang! Bang!"
Another photo shows Mr Donaldson with his arms around his two sons Sandy and James. The caption says "The middle men in red shirt is DAVID WILLIAM DONALDSON my target !!!"
Mr Donaldson said the threats had been up for quite some time.
James Donaldson said he was frustrated that things haven't moved as swiftly as he expected.
"I expected everything to move quickly but the storm has settled and everything has just stopped.''
He said he didn't expect there to be a holdup, especially considering Simon is an overstayer.
He said he thought Indonesian officials would have been more cooperative in trying to get Simon out of the country.
"It should be black and white, but in Indonesia it's grey.''
