Hi Jan,
I reckon all the Richters I found in the Qld BMD's are yours (only half joking). There are quite a lot of them though!
Righty ho, here goes:
from the Assisted Immigration book 1848 - May 1884
RICHTER
Hermann age 9 (I think this might be your Herman)
Johann 50
Louise 11
Pauline 9
Wilhelm 13
Gustav 3
Ernst 40 (I think this might be his father)
Ernst 6
Caroline 39 (I think this might be his mother)
Carl 5
Anna 46
Anna 8
Auguste 16 (female)
all on the ship Susanne Godeffroy
arr Brisbane 6 Sept 1865
IMM/113 p 62 Z 1957
(the arrival date and reference information appears to be incorrect as I could not find this family or this ship on this film).
However there IS a Passenger List Book for the ship Susanne Godeffroy which departed Hamburg 6 May 1865 and arrived Brisbane 8 September 1865, and your family are listed on there too.
In the Passenger book is also listed where they were from. All were from Bernau Prussia as you thought, except for Johann age 50, Anna aged 46 and Anna aged 8. They were from Weddingstedt, Holstein. Now with all those Richters on the same ship at the same time, it looks like two related families.
I had a look for Herman's death and found that he died 15 Oct 1824 and his parents are Ernest Richter and Caroline Koch.
In the Dunwich Asylum book I'm afraid there was very little information. Two films were listed by his name - I looked at both of them, but they gave little information either. Unfortunately there was no date or reason for admission. This is all I found in their register of deaths:
Year no: 133
Register no: 88/24
Age: 69
Date of Death: 15-10-24
Cause of Death: Senility
No of grave: 680
I did not find a will for Herman or Elizabeth. I found an intestacy on film for Anna Auguste Richter (maiden name Wisseman) d 31-10-1914 which gave very little info except that she had no children.
I found another intestacy on film for George Richter, "selector", late of North Rockhampton, died intestate, lawful eldest son George Ernest Richter, another son John, married daughter Maria Magdelina Werner.
As I said there are many Richters on the BMD fiche. I don't know if you already have the following:
Elizabeth Caroline Richter
d 9-10-1913
father: Robert Roberts
mother: Emma Campton
Hermann Charles Ernest Richter married Elizabeth Caroline Roberts 3-3-1884
Children born to Hermann and Elizabeth:
Elizabeth Jane 10-9-1890
Margaret Annie 4-2-1893
William George 2-6-1898
Edward Thomas 4-8-1895
Emma Caroline Margaret 15-8-1884
Louise Pauline Augusta born 6-12-1886 died 26-3-1887
Robert Gustave 26-6-1888
I also found this and wondered if this may be the death of Herman's father Ernst?
Ernst Wilhelm Richter
father: Johann Friedrich
mother: Johanne Christine Adler
After I got home I had a thought - I wonder if Herman can be traced through the electral rolls to give an idea when he went to the Asylum? I think I need to know his address for that though - or a suburb at least.
Let me know if you need more lookups - I'm going away soon but would be happy to help again when I return.
All the best.