Hey Rambo34k as I mentioned on your introduction thread, I am so very sorry that you are going through this.
I confess to not having a lot of experience with predators, only having to deal with the very rare stray dog and/or overweight, pampered, neighbourhood pussy cats. However, I was hoping that I might be able to help you.
I am not familiar with a “deer mount” but if my research is correct, it is for a taxidermied deer? Please do not take this the wrong way because as I said I am not sure what a “deer mount” is but I think the safety of your live chickens would take precedence over the dead deer?
In the meantime, I have a couple of suggestions. Do you have anything on hand that you could lay around the outside or inside of the coop? Sleepers, pavers, bricks, rocks .. anything to temporarily deter digging in the short term?
Is there anywhere else your remaining 6 girls can sleep until you get this sorted? A shed with a solid floor, a basement, a bathroom etc?
This predator knows where your chickens are and unless you can stop it getting into the coop immediately, you will need to get them out if you want to save them.