I'd say tank controls ironically enough just aren't great on keyboard in a top down game, it's a nice idea to go for but it doesn't really work too well in practice. I think leaning off the realism and either having turning on the spot, or just full on removing the tank controls and using traditional movement, would be ideal for improving the movement feel.
Same goes for the aiming, I feel like moving to something like mouse aim would feel best, and lead to a more fast paced gameplay style, otherwise having some aim guide would help a lot, since needing to watch the tank cannon makes it overly difficult to hit a distant small target.