It's been a long time since you've posted here your search for Ernst. I'm looking for the same thing. Most of my family were born in Surabaya and Madioen and moved to Europe, to the Netherlands. I hope that you have more information since you've posted here.
My grandfather (Harie Eduard Ernst) was born in 1907 in Madioen. His father (Willem Eduard Ernst) was born in 1871 but I still don't know if his place of birth. I have more names of people who were born after 1871. If you need more information or have more info for me, please contact me here or directly via e-mail.