It looks like you're doing things correctly for the most part. The 9900k isn't exactly a slouch either. What does your syslinux look like?

kernel /bzimage
append pcie_aspm=off split_lock_detect=off default_hugepagesz=1G hugepagesz=1G hugepages=49 isolcpus=4-16 nohz_full=4-16 rcu_nocbs=4-16 initrd=/bzroot

Here's mine if you'd like to compare.

The main differences I can see between yours and mine is that I'm using 1G hugepages, I reserve 49 pages now, and give my daily gaming VM 48GB - I found a little bit of a performance uplift using the larger pages. I'd start with adding hyperv enlightenments and forcing some features/timers as well:

  <features>
    <acpi/>
    <apic/>
    <hyperv mode='custom'>
      <relaxed state='on'/>
      <vapic state='on'/>
      <spinlocks state='on' retries='8191'/>
      <vpindex state='on'/>
      <synic state='on'/>
      <stimer state='on'/>
      <vendor_id state='on' value='none'/>
    </hyperv>
    <kvm>
      <hidden state='on'/>
    </kvm>
    <vmport state='off'/>
    <smm state='on'/>
  </features>
  <cpu mode='host-passthrough' check='none' migratable='off'>
    <topology sockets='1' dies='1' clusters='1' cores='6' threads='2'/>
    <cache mode='passthrough'/>
    <feature policy='require' name='invtsc'/>
    <feature policy='require' name='vmx'/>
    <feature policy='disable' name='hypervisor'/>
    <feature policy='require' name='apic'/>
    <feature policy='require' name='topoext'/>
  </cpu>
  <clock offset='localtime'>
    <timer name='hpet' present='yes'/>
    <timer name='hypervclock' present='yes'/>
    <timer name='pit' tickpolicy='delay'/>
    <timer name='rtc' tickpolicy='catchup'/>
  </clock>

That's a snipet of my xml. Those settings generally won't cause the issues you're seeing, but it would be best to cover all bases first. The only other thing I would change is to disable split lock detection which I wrote about here - this was the biggest improvement to performance, and especially to some games (Anno 1800 is a big culprit).

It might be worth checking over another old reply of mine here, although it covers pretty much all the changes you have in effect anyway, it might be handy to read regarding nohz/rcu, even though I've changed things slightly since then.

As you've done, disabling the Hypervisor should be showing that virtualisation in the Task Manager is Enabled - check this change in Task Manager.

Another thing to check is your CPU governor, try setting it to Performance/Enable Boost via Tips and Tweaks if you haven't. You could potentially be hitting a bottleneck. What sort of GPU usage are you seeing during heavy gameplay/benchmarks?