WOW - what a great job and well worth the wait! I am not going to print it out here again, as there are not too many things I would change. I will just print the sections that I think need a bit of work.

Pet commissions were not very popular in the profession because it was difficult to reproduce the lifelike qualities the poor creature would have had in life, no matter how accurate the physical mount would be, and customers were often not entirely satisfied.
This sentence is too long and could be split into two.

Mavis was a quiet young woman. Very interested in nature and natural ways of living.
This could be one sentence, with "who was" after woman.

I dyed my hair and wore it a bit longer. And I bought some tinted contact lenses to change my eye colour.
You shouldn't start a sentence with "and" so you could make it I dyed my hair and wore it a bit longer, buying some tinted contact lenses to change my eye colour.

I quickly overpowered her and bundled her into the van where I bound her and gagged her.
bound and gagged her - no need for using her twice.

I was completely unnoticed and this stage has been completed with total success.
"has been" should be "was"

Once inside the cottage, I dragged the girls into the main room where I had made preparations for transporting them into Canada. When they saw the coffins, they almost passed out with fear. I gave them no reason to doubt they would die. I picked them up one by one and placed them in their coffins.
Nothing wrong here, but I did wonder when the girls had their gags and bindings removed, as later when the coffins are checked, they are unbound
I was confident that I could make the girls live for a very long time. And I saw no reason why I should give them anything to relieve their suffering.
Again just the sentence starting with and. Just join the two together or even just leave and out all together.

The stake penetrated his back passage, his bowel and his stomach, and ran up through the cavity in his chest missing his hear and lungs.
heart

Once again, well done on a great job! You have put so much effort into this and I really enjoyed it. I will have to get H Dean to have a look too, but I am sure he will enjoy the twisted background you provided.

I am kicking you up to level 3. Thank you for all your hard work and good luck with your future writing endeavours.