The Flashpoint Streaklight 360 will do highspeed sync with their triggers from what I know. As will the Flashpoint Rovelight 640 with their proprietary HSS trigger (though it is really hypersync). Your shot looks good, well balanced with the ambient.

If you overpower the ambient light with the flash, you can stop action with the flash. The lower the power, the faster the drop off. With the Einsteins, at 1/256 power, action stopping equivalent would be 1/13500, at full power it is around 1/500 I think. If you can overpower the ambient with 1/2 power, you would be at the equivalent of over 1/2000 shutter speed. As has previously been mentioned, Einsteins do not do HSS (high speed sync), they do Hypersync, which is basically timing the flash AND light fall off to fall in line with the opening of the shutter. This can only be achieved with using a Pocketwizard Mini TT1 or Flex 5 on your hot shoe and any number of Pocketwizard remotes attached to your strobe (Plus II, Plus III, MC2, etc). The negative part of this setup is that the Einstein would have to be set to full power, but you would be able to shoot above your cameras sync speed (I have had success up to 1/8000). I have found that this setup is overkill for gyms. The flash really becomes noticeable and if you are trying to shoot at a shallow depth of field, there is too much light. This set up works much better if you are trying to overpower the sun for outdoor shots.

The dock is only compatible with their current Art, Sport, and Contemporary lenses. It is not compatible with any other lenses. For less than the price of shipping your lens to Sigma, you can get a dock and update firmware and make focus adjustments at home.

When I shoot wrestling, I am mainly using a 70-200 f/2.8 lens. Settings are usually f/2.8, 1/ 640, iso 4000-6400. I shoot RAW and post process through Lightroom CC. Looking at your image, it just looks like it is just lacking some post processing. Another thing to think about is noise will not show up as much if printed since the printing softness tends to soften the image and the noise a touch.

Like Macronaut stated, it doesn't matter whether you crop in camera or in post, you will get the same results.

Another advantage of using the D810 in crop mode vs the D7200, is if you have the battery grip and AA's or the EN-EL18 battery, you can get 7 fps vs 6 on the 7200. Comes in handy for birders or sports shooting.

This is a short video created by former Sports Illustrated photographer Bill Frakes that was done exclusively with the Nikon D5.
http://blog.strawhatvisuals.com/2016/01/05/my-nebraska-and-the-nikon-d5/

I had a similar scenario with the Tamron 150-600. I thought that the D7200 would give me better images than the D810 in crop mode. I was wrong. Even though the D810 only gives you a 16 meg image, I felt the images were better. Even if you shot full frame and cropped, the image was better. I think it is because the pixel pitch of the D810 is larger than the 7200 which gives it better signal to noise ratio and more dynamic range (4.87up vs 3.89up). I wouldn't recommend a teleconverter if image quality is what you are seeking.

If you were going to make a movie, it might be a problem. I don't see myself recording my kid's plays or anything like that with a camera like the D5, but doing little snippits here and there to produce a commercial or video montage would work. The D500 uses an extreme crop of the sensor to shoot 4k so that might be a reason it is able to record longer (less information being transferred).

I for one am extremely excited for the unproven D500. For the type of shooting that I do (sports/ action), it will compliment my tool chest nicely. Not everyone needs 10 fps, but it helps me get the moment (s) that 6 fps misses. Don't get me wrong, I absolutely love my full frame bodies (D4, D810, and D750) but I never found the D7000 series was up to the challenges I face when shooting sports (focus speed, fps, build). Each body has a purpose. Can they overlap, certainly. But each is designed for different purposes. D4 for low light, action. D810 for large prints, landscape, portrait. D750 for a second or third body for my sports and portrait shoots. It is a jack of all traits but master of none type body. Now the D500 will be a compliment to my D4 for sports action to be able to "get more reach" out of my lenses without having to crop and lose resolution afterwards. Complaining about the D500 not having the value of a D750 is like saying the new Camaro doesn't have the value of a Suburban. Two totally different vehicles just like two totally different cameras.

If shooting in a dark gym, an f/2.8 lens or faster is required. For wrestling, a shutter speed of 1/500-1/800 is usually sufficient to stop action. You will have to bring up your iso to achieve these speeds. I am going to guess you will be in the 4000-6400 iso range. The more you fill your frame with your subject, the noise becomes less of an issue. Hope this helps.

(Download)

I have Remask and it does work quite well. As with any other extraction method, having good edge contrast makes it more accurate. Try the free trial to see for yourself. If it is not currently on sale, it will at some point and go for as much as 50% off.

Have you tried back button focus? I would say close to 99% of professional sports shooters use this method.

Since the moon is thousands of miles away, setting your focus ring to infinity usually works if autofocus is not grabbing it. You didn't mention whether you were on a tripod or not, but could it be camera shake that is causing the unsharp image? I am assuming that you were racked out to 200mm when taking this, so your minimum shutter speed should have been 1/320 if hand holding (1.5 x focal length). Another thing to think about is since the moon is thousands of miles away, no need to shoot this at f/22 since depth of field is not an issue. At f/22, you run into diffraction which will affect your image. Most lenses are sharpest between f/8 and f/11. So by opening up your aperture, you can easily increase your shutter speed. With the settings you had, you could have easily shot this at f/10, 1/320, iso 200. Hope that helps.

True. But once again, in order to make sure that the plane of focus does not change, a tripod would be needed wouldn't it? Also you would need specialized equipment that most don't have.