If i polymorph my familiar into humanoid shape, give it a weapon and cast "Emblem of Greed" on its weapon using deliver touch spells, is the familiar able to use the weapon and does its base attack bonus change while wielding the weapon?
Similarly, if I hold the weapon, does my familiar's base attack bonus become my new base attack bonus?
1. When you deliver a touch spell via your familiar (share spells aside, since this spell isn't compatible with it), you are still the caster. All of the parts of the spell that say "you" refer to you, not your familiar. The weapon would become a +1 flaming glaive (or whatever) appropriately sized for you; you would be proficient with it; and you would get to use your caster level as your base attack bonus when wielding the weapon. Your familiar would only get the benefits that don't apply specifically to "you"--namely the use of a +1 flaming glaive (or whatever). Your familiar would use its base attack bonus, and if your familiar is not proficient in the use of glaives, it would take the usual nonproficiency penalty.
2. When you hold the weapon, you use your caster level as your base attack bonus. Your familiar's base attack bonus doesn't come into play at all unless it's the one attacking.
Hope this helps!