Thanks! About infantry hit rates, note that 400m is at the limit of effective range for many weapons and that the game assumes that infantry, unless they are moving fast, will try to avoid fire by lying down. So with that in mind, it makes more sense.
edit: regarding your question about the scenario, IIRC the "trick" is to use mortars and artillery to separate the German infantry from the heavy tanks and then close assaulting them with infantry in the factory.
edit2: also note that a new patch was released recently, which includes several new (allied side) scenarios by myself, set in 1945, as well as a new Russian campaign I made a while back, aimed at beginning players.