How you stated it can have different interpretations. The one about eating I thought would be kind of loose and come down to sellers honesty (which it could also be reworded as “has taken 5 consecutive meals in captivity without refusing”). “Fully established in terms of husbandry” can have many different interpretations. You would need to have something solid to actually state that. Fully established husbandry wise can mean not refusing food (which falls under the feeding category), not getting sick (visually), the last shed was complete, layed a clutch of eggs, the classic “it ate so it must be happy”, etc. It all falls down to the sellers honesty which is why you will need a baseline that can only be interpreted one way.
For the record it was one more word.