Reading through this…
So, first off, I think the category is a bit too broad. You may want to focus on a specific recovered instance or set of instances, and then allude to additional instances yet uncontained, dead, etc. Handwaving the containment procedures into a nonexistent document doesn't add much. Especially since -D is 'everything else'. Having a handful of specific instances would be significantly better than broad categories.
Rum N Napalm's advice still holds - there's no need to use obscure terms when normal would suffice. For example, 'non-autochthonic' should be replaced by 'nonstandard' or other term. In addition to that, there's a lot of words that either misspelled or make little sense in context. For example:
> SCP-XXXX-C: Appearance consists of an amalgam of human and animal nature with non-autochthonic characteristics taken penance over those of human nature
'Penance' means 'voluntary self-punishment inflicted as an outward expression of repentance for having done wrong'. It doesn't make any sense in this context.
Anomalous characteristics have been observed as well in most instances, the majority of which are automatic/non-consensual by the instance, with controllable/non-automatic traits being in the minority.
'as well' is entirely superfluous, and should be split into two statements. First being that some properties are anomalous, the second being that properties are generally uncontrollable.
"Salability" means 'suitable for sale'. Does not make sense in context.
The Journal is OK writing wise, but the last bit being written 'frantically' is a little comical. His comrade just got attacked by invisible monster - let me hastily write this down before I do anything! Either use a video/audio log transcript, or an after action report. Journals are not real-time documents.
My suggestion: Concept base is OK, but focus on specific instances rather than broad categories. Go through this with a grammar and spell check - lots of things are in the wrong form, adjectives where they should be nouns, etc. "herd" in place "heard" was another I saw a lot. If a word doesn't look right, it probably isn't.