Col

That's what happens when you use wide apertures. If you want more of your image to be sharp use a smaller aperture.

Yes, if you use the Nikon trigger the Godox Fuji specific flashes will work just as if they were Nikon specific. You can also control them with a Godox Nikon specific flash by using it as a master on camera in place of a trigger. Most of the latest Godox flashes have this capability.

You can get a device to sit between the camera and the flash that will protect your camera from the excess voltage. I use a Wein Safesync and it is very reliable but I don't know if they are still on the market.

You can't change flash settings from the camera. You change flash mode on the trigger and the flash will use that mode, assuming that you are using a flash with TTL capabilities.

I have noticed the odd black frame when using my XT-2; nowhere near as many as you are reporting though. I haven't been worried because I'm not aware of missing any shots. My best guess is that they are occurring when I turn the power off but I will try and keep a closer eye.

All cameras will respond to infra red light. If you take infra red photos the way you describe your exposure times will be considerably longer for a given ISO. This is because not only does the infra red filter block almost all the light in the visible spectrum but there is a filter on the camera's sensor that blocks infra red light so not a lot of the light entering your lens reaches the sensor. At least the XT-2 has an electronic viewfinder so you should still have a reasonable view for framing etc. If you just want to try infra red photography the cokin IR filter will be OK. Just be prepared to either bump up your ISO (a lot) or use a tripod. If you decide to get into infra red photography, you might be better buying a body that's been converted for IR or paying for a conversion. IR conversion is basically removing the IR blocking filter from the sensor. You can choose to replace the IR blocking filter with an infrared filter at the sensor (that's what I have done) or you can just remove the IR blocking sensor and replace it with clear glass and use an IR filter on your lens. There are pros and cons for both. Google infra red photography to find some websites that can provide more detailed advice.