It might also help to add a hidden state to the VM so win10 doesn't know it's a VM and freak out, you can do this in the same xml as the one you use to pin the cores. Add the following line to the "features" component after "acpi"
As @stenstorp said you need to leave resources for the host to use, leaving threads doesn't really give control to the host, so a good beginning configuration would be splitting the CPU resources in half giving the host and guest 3 cores and 6 threads each, you'll also want to split you memory in half also if your not doing it already.
If this works and your errors/BSDs go away you can try and bump up the number of cores to 4 and 8 threads leaving the host with 2 cores/4 threads, I run a similar setup with a AMD 8370 giving the guest 6 cores leaving 2 for the host and it has worked for well over a year with no issues, starting out on Win 7 (as a guest) and now running Win X.
With that taken care of it may also not be a issue with how you have things setup in vert-manager /QEMU, it may be totally unrelated...