The main difference here is that the 25-pounder uses a crew while the B4 (and other howitzers) are team weapons. A crew is purely visual and doesn't represent any real "unit", so the crew members can't die. A team weapon is operated by entities just like the ones in regular infantry squads, so they can attack and be attacked.
Having both the infrared and the normal model of the StG44 in the ABP file causes this issue. There is no known workaround, so you need to decide on one of them.
This was an upgraded version of the T34 which incorporated fixes to address the concerns of crews in the field, and was basically a serialization of the popular field-mod that had arisen. Modifications were introduced to allow the 75mm main gun to fire with the launcher attached and retain its original elevation range. To achieve this, the elevation arm was attached to the small metal extensions near the base of the gun, found on the M34A1 pattern mantlet.
The E1 also replaced the plastic tubes with magnesium ones and was equipped with an easier system cut-off for simpler jettisoning. The T34E2 was almost identical to the E1, but had an improved firing system. It was one of these models that received the nickname ‘Calliope’ when it was witnessed firing, and from there, the name stuck.
So it depends on the model. But having it be able to fire its main gun is definitely justifiable. Not saying it's a good idea though - I'll leave that to the balance experts.
280MP is too cheap for a unit that can get double Schrecks. I'd rather see them with two PzB39 AT rifles and a Panzerwurfmine AT grenade (using the Soviet RPG-6 model).
From what I have read, Red Army officials were quite sceptic about handheld AT weapons supplied from the US and UK. They were quite happy with their PTRD and PTRS rifles and wanted something with similar range. That seems to be the reason why the Bazooka did not see much use and it might also be the reason why the PIAT wasn't used at all.
Hit chance is accuracy multiplied with target size. Missing at close range is unlikely, but possible. Repeatedly missing is therefore even more unlikely, but still possible.