Alright I applied the changes and...
*** Error(s) finalizing the creature RHINOCEROS
RHINOCEROS:FEMALE:right front hoof, layer 1: Tissue HOOF was not found, using first tissue instead
RHINOCEROS:FEMALE:left front hoof, layer 1: Tissue HOOF was not found, using first tissue instead
RHINOCEROS:FEMALE:right rear hoof, layer 1: Tissue HOOF was not found, using first tissue instead
RHINOCEROS:FEMALE:left rear hoof, layer 1: Tissue HOOF was not found, using first tissue instead
RHINOCEROS:MALE:right front hoof, layer 1: Tissue HOOF was not found, using first tissue instead
RHINOCEROS:MALE:left front hoof, layer 1: Tissue HOOF was not found, using first tissue instead
RHINOCEROS:MALE:right rear hoof, layer 1: Tissue HOOF was not found, using first tissue instead
RHINOCEROS:MALE:left rear hoof, layer 1: Tissue HOOF was not found, using first tissue instead
*** Error(s) finalizing the creature RHINOCEROS
RHINOCEROS:FEMALE:right front hoof, layer 1: Tissue HOOF was not found, using first tissue instead
RHINOCEROS:FEMALE:left front hoof, layer 1: Tissue HOOF was not found, using first tissue instead
RHINOCEROS:FEMALE:right rear hoof, layer 1: Tissue HOOF was not found, using first tissue instead
RHINOCEROS:FEMALE:left rear hoof, layer 1: Tissue HOOF was not found, using first tissue instead
RHINOCEROS:MALE:right front hoof, layer 1: Tissue HOOF was not found, using first tissue instead
RHINOCEROS:MALE:left front hoof, layer 1: Tissue HOOF was not found, using first tissue instead
RHINOCEROS:MALE:right rear hoof, layer 1: Tissue HOOF was not found, using first tissue instead
RHINOCEROS:MALE:left rear hoof, layer 1: Tissue HOOF was not found, using first tissue instead
*** Error(s) finalizing the creature RHINOCEROS
RHINOCEROS:FEMALE:right front hoof, layer 1: Tissue HOOF was not found, using first tissue instead
RHINOCEROS:FEMALE:left front hoof, layer 1: Tissue HOOF was not found, using first tissue instead
RHINOCEROS:FEMALE:right rear hoof, layer 1: Tissue HOOF was not found, using first tissue instead
RHINOCEROS:FEMALE:left rear hoof, layer 1: Tissue HOOF was not found, using first tissue instead
RHINOCEROS:MALE:right front hoof, layer 1: Tissue HOOF was not found, using first tissue instead
RHINOCEROS:MALE:left front hoof, layer 1: Tissue HOOF was not found, using first tissue instead
RHINOCEROS:MALE:right rear hoof, layer 1: Tissue HOOF was not found, using first tissue instead
RHINOCEROS:MALE:left rear hoof, layer 1: Tissue HOOF was not found, using first tissue instead
It seems I forgot to add [USE_TISSUE_TEMPLATE:HOOF:HOOF_TEMPLATE]. That has been corrected. It should work now then.
As for number 5, thing you want to take a look at is [POPULATION_NUMBER:X]. Increase the number, and more rhinos will spawn per biome where they appear. Also if you are having trouble getting rhinos to spawn at all you might want to consider adding the [UBIQUITOUS] tag, which will ensure that they appear in every tropical savanna, grassland, and shrubland, instead of just appearing in some of them.
Their vanilla population number is curretly [POPULATION_NUMBER:15:30] so Im buessing that means 15-30 per biome. Will the [UBIQUITOUS] tag make them too frequent or have any negative effects besides simply ensuring that they will certainly appear wherever they can appear?
Once again, many thanks.