[Edi]

1) No. This is in the FAQ.

2) All melee weapons. They get the "bless fire" weapon added to them.

3) Flaming arrows affects longbows, short bows, crossbows, arbalests, slings, chakrams, javelins, shuriken and boulders, not sure about throwing axes. It should also affect banefire bows, but I'm not sure about other magical bows.

4) Units with heavy armor and/or good shields usually suffer less from Blade Wind.