Not sure about that lack of hit sounds, is it happening in all tanks or just the new ones (wheeled) ?
As for the sound volume you have no choice but to play with the sliders in the game menu, try to lower some of them if they are too loud.
The battle hits viewer has own button in hangar the same way you had in previous modpack. Next to the notification channel.
To check the rest of issues I would need to see logs, see my signature.