I think you are expecting a little too much from your equipment.
The hawk picture is a really extreme crop. It is slightly underexposed which will accentuate any noise, particularly in the plain sky. Although the humming bird crop is less extreme it is still a significant crop at 3200 iso and there is a limit as to what you can realistically expect at that speed.
I use the D500 with the 300mm PF and the 1.4tc. I have the 2.0tc as well but seldom use it as it is not as sharp as I would like. I do crop a lot with the 1.4tc but seldom get good results with very large crops at high iso.
This Spotted Flycatcher was taken at 4000 iso in very dark woodland. It is a crop from about 1/6th of the original file. It's not too bad but I wouldn't really want to crop any further in order to try to see more detail. No doubt someone with better post processing skills than me could produce a better result but there are limits as to what is technically possible.
If you are going to crop a lot it is best to try to keep the iso as low as possible and to ensure that you are not underexposing at all.