Pushing can be a gamble, everyone will have their favourite method.
Your images could look contrasty for a many different reasons, exposure, development and scanning all can have an effect on the final look.
The last shot where you have most contrast is very underexposed, even a four stop push wont help here as you have exposed for the highlights.
I think you need to meter a little more accurately.
Firstly set your meter to 1600 (presuming 2 stop push of 400 film)
The trick is to meter for the point where you want emerging detail, that is the point where things just appear in the shadows. Then stop down two stops (no really because your meter sees 18% grey you need almost black)
Next develop your film for pushing, you can use a mild speed increasing developer like Microphen/Xtol/Tmax etc which will ensure good shadow detail and grain.
Here is Neopan pushed one stop with the above metering method (developed in Rodinal)
You can go further, these are delta 3200 at EI 25,000 developed in week rodinal with low agitation.
The key is to expose for emerging detail minus two stops, the rest should fall into place.
Mark