[Imp]

Well I think the tone gives it away, you wont find these results happen.
Just how often does the AI direct fire its arty anyway & from my experience mainly does vs vehicles with about as much success as I have.

Z fires been done to death & yes to potent more on placement than effect though but cant see how to improve without a new game engine. Sometimes you can target hexes you realy shouldnt be able to so dont.

On the crew I think you are raising a few issues.
The first is that the unit recovers from retreat status in your turn catching you out.
Seems quite acceptable to me & its fairly rare & probably triggered by a nearby freindly doing something. When it happens its your fault anyway for not suppressing enough in the first place.
Infantry without dedicated AT weapons had better be high exp morale?or they will run rather than assault
Crews (no idea how many men dont look) will sometimes attack a vehicle if it moves adjacent, the chances of a vehicle kill is nearly zero might immob an open top if very lucky, standard result is probably both units suppresed. Cant say what happens with riders running up against a crew as dont do but that result sounds about what I would expect from having riders get caught out vs other units. They die fast 3/4 or whole unit wiped out seems fairly common when I target them.