Hi,
1)
we use the when it is clear which thing or person we mean (general rule). You would also write: The sun is shining even though you had never meant the sun before. 'The establishment' in your sentence is clear for everyone which applies to the most of the abstract words like believe, development, etc.
2) hereby = by mean of this
I hereby declare you man and wife.
3) hereafter, we use this one, when we want to refer to in some subsequent parts of the text
The XBC Company, hereafter the purchaser
The purchaser decline that ...
4) hereinafter = use like hereafter, for subsequent parts
5) hereto = to this writing or document
The copies hereto attached show that my client never purchased the house from your client.
6) ... ?