Yes. Ive had my D500 with nikkor 200-500 on it and its fine. its a great tripod. 

Yes. I have the same lens and adaptor on my Sony a7ll and it works beautifully. The m42 is also known as the 'universal' mount as other 3rd party camera and lenses also used it. I own 6 other K&F e-mount adaptors to different lens makers (ltm, MD, CF/CD, Nikon) and they all are well built with a nice snug fit. Highly recommended. 

The adapter is designed for Nikon lenses, including D mount. If the Tamron fits the Nikon D80 it should work. As for the lack of aperture ring on the Tamron ... not sure about that. Perhaps the Nikon D80 has an in camera aperture selection. 

the bag can hold canon 500mm f4 lens, 

I actually have not received this adapter yet. It's shipping from China. Don't think that was disclosed in the ad. However, I do not believe this is for the Pentax Q body rather for digital and film cameras that take the Pentax K mount in its many variations. So I'm expecting to be able to mount my Leica M mount lenses on my digital and film Pentax K mount cameras, no autofocus or relay of exposure information, only to be used with manual focus and exposure.