That must have been a wonderful trip, with some beautiful shots. You have a first class camera also. I hope you will permit a few comments.
I would not worry too much about the dust on the sensor so long as it only shows up at very small apertures like f22. Set your camera to do automatic cleaning every time you turn off the power, and do not try any mechanical means of cleaning unless you are an expert in a clean environment.
There is no need for such tiny apertures in subjects such as this. One of your images was at f36! There are very few good indications for this.
A lot of wildlife photographers use Aperture Priority as the release mode most of the time, and set the Aperture to a stop or two below the widest. In your 300mm f4, that would be f5.6, 6.3 or even f8. That lens is very sharp wide open, but stopping down a bit gives you an increase in depth of field, and you do not have to adjust it very often. (Stopping down much below f11 begins to casue diffraction which reduces sharpness.)
Then the camera will choose the shutter speed.
Letting in more light means the shutter can be faster and the iso lower. With the d800 you can also move to manual and set both f number and shutter speed, such as f6.3 and 1/2000, and set iso to Auto. The camera will then manage the brightness of your results by adjusting the iso. This might work well where you have lots as light, as on this trip. And if you always shoot RAW you can rescue a lot of exposure problems later.
Most of the time for wildlife I use a single center point for focus, because it is hard to predict what point the camera will choose if you use any of the multiple point options. Be sure the lock lever is in the locked position.
With settings like these more of your pictures will be as good as the one you posted today.