Nikon 300f4 is f5.6 when used with TC. Its 420 f5.6 where 200-500 is 500 f5.6 but maybe not sharp till 500mm .
So I dont give advantage of focal length to 200-500. yes VR is something special on 200-500.
If I can carry 1.8KG Sigma 150-500 so I can carry a 2.2 KG 200-500
Nikon 300mm f4 Non-VR - Nikon 300mm f/4 AF-S Review
Nikkon 200-500 VR - Nikon 200-500mm VR Review
I'm not sure, but a camera upgrade will help you too. D7000 is good, but the low light performance of D7500/D7200 is much better(both of them use Sony sensors if I'm correct, D7500 is practically less fancy D5). Better low light sensitivity = Ability to stop down.
Also, there is a huge difference for optics when moving from 16 to 24mp (specially for certain lenses). One my friend's NEX-7(which was one of the first in 24MP class) had trouble utilizing the old E mount lens lineup(pre 2013), images were just not sharp enough.
And honestly, if you are thinking of going big, why not 150-600mm f/5-6.3 (from Sigma and Tamron)? I mean, ultimately you will end up with a big and expensive, but do it all lens, instead of owning 2 separate lenses for mid and long end.
I'm thinking of buying Sigma 50-100mm f/1.8 ART with MC-11 adapter soon...let's see how it will work without optical image stabilization. Ultimately, I will reduce my system to just 2 primary lenses, Sigma 18-35mm f1.8 and Sigma 50-100mm f/1.8 ART with a backup prime. Can't be bothered with too many lenses.
I was thinking, and finally created a long term(next 5 years) roadmap for purchases:
Going to sell: Sony A6000, Zeiss 16-70 f/4 (Not at all good), Kit lens
APS-C
Sony A6500 successor + Sigma 18-35mm f1.8 + Sigma 50-100mm f/1.8 ART + Sigma 30mm f/1.4 Contemporary + (Sony 16mm f/2.8 + VCL-ECU1 = 12mm)
Fullframe
Sony A7R ii successor + Zeiss Batis 85mm f/1.8 (This option will be used mostly with portraits. I love APS-C for everything else)
Compact
Fujifilm X100F or Sony RX100 (X100F isn't exactly compact...but is just beautiful)
Edit: And a second hand or fully manual cine lens. I used my friend's Fujinon MK series lens and it was...different. I some time help my friends with their video projects, and a lens like that will certainly help, specially with the lack of focus breathing and ability to hold focus.