1. A tailwind causes less air over the wing reducing lift. IAS is proportionate to the air around the wing. No air - no IAS.
2. IAS will decrease with a tailwind - refer to 1.
3. Not sure what book you're reading but that's very vague. Firstly, you wouldn't go anywhere near a microburst. If you're unfortunate to encounter one, you would reduce your speed to the turbulence penetration speed or worst case scenario and dropping like a stone, pitch right up just before the stick shaker (that is possibly why the book's author mentions a pitch up).