HI Triumbike!
Uh what version or Steel Panzer mod of SF are you playing?Because the lack of reticle for the Panzer IVF was an issue with the SP 1.4.With the Beta 1,5 that issue has been solved!For the SP 1.4 there an English language fix which is available.
The issue of aiming.Why don't you set your control to move the turret with the up and down and right and left keys on your keyboard instead of using the mouse.It's less arcade and it gives you better control.It may be that your mouse sensitivity needs to be toned down?I have reset the key and I don't as a rule m use the mouse to aim anymore.You can go into the options menu uin the controls section and you can reset your keys and also adjust the sensitivity of your mouse of you feel like using it for aiming.
As for your tank shooting by itself it may be that one fo the default keys for shooting is defaulted to your mouse pad.This would explain why every time your touch your mousepad(laptop) or your mouse your tank shoots.Again check the control keys and may be , like I do, use either the enter key as your primary shooting key and the spacebar as your secondary one.This way no accident!