You need to define exactly what your priorty style of shooting is now and will what it will be for long term. You indicated it will be a longggg time before you can invest again in expensive gear.
You are trying to upgrade everything you got and that will be tough to do and stay within your budget.
From what I read you are into landscape and nature and would like to expand on to portrait. To upgrade your landscape lens, I would strongly consider the Tokina 11-16. A sharp image taking build like a tank lens and 2.8. I would also give some consideration to the Nikon 12-24 f/4, a few hundred more than the Tokina, but a more versatile lens. I put them in that order only because of cost. If it were not for that I would put the Nikon first. Theres also the Tokina 12-24 f/4 $100 less than the 11-16 with build in lens motor. Another great landscape lens. For landscape, the f stop is not as important as it is for nature and portrait.
Sell your 70-300 for $500? You can buy a refurbished one from
B&H for $350. Or buy a Nikon 55-300 f/4.5-5.6G VR for $360, new.
To settle on a portrait lens, I would buy the Nikon 85mm f/1.8D for $430 and never look back! Regarded as one of the best prime portrait lenses. Or save a little more and buy the Nikon 50mm f/1.4D for $330. ANother great portrait lens. Both of these lenses produce very sharp images even in low light.
So let's assume you settled for the Tokina 12-24 f/4 and the Nikon 50mm f/1.4D and you spent $830.00. Thinking of your budget you may have around $1200 left? I would keep the 16-85 f/3.5-5.6 for everyday up and down the street shots and sell the 70-300 and now you got enough to buy an excellent used Nikon 70-200mm f/2.8 VR1 that you will never regret purchasing. Explore all avenues and you will find one, I did.
Then you are set! Of course, somewhere down the road, you may want to pick up a Nikon teleconverter 1.7 for the 70-200 for a couple hundred or so.
Good Luck!