So, quickly, here's how I'd fix both:
- A shield gives a 1-point defensive bonus, as usual.
- Using two weapons doesn't increase your number of attacks or your damage, it just adds +1 to your attack roll, or gives you something to parry with (same effect as shield.)
- "Shields Shall Be Splintered", of course, but modify chance of breaking based on material and shield/parry weapon size compared to attacking weapon.
- Shield bash is just another weapon: normal attack, 1d6 damage.
- Use shields to block missiles, if you can see them coming; minimum AC3 or the standard armor+shield.