Not really, just put a limit of one bomber per player with limited spawns per match and also reduce the ridiculous bombloads of planes like the Ju-188 and A-20.
No need to add more anti-infantry vehicles in an infantry focused game.
No they are not.
They do because they are also given AP ammo (which makes sense in a fully vehicles-oriented game).
Even there tho, you can’t just spray a tank effortlessly with a SPAAG and kill it outright. In most cases (except a few OP specimens), you have to ambush it and get a shot at least protected areas (side/rear), providing your have AP ammo.
In Enlisted, SPAAGs could work as an alternative to tanks, trading antitank power (which would be low to none, depending on the ammo availability) for increased anti infantry and anti air potential.