" 2) If my life force is in the magic jar (and not in any body) can I still cast spells from the jar's location (provided I have access to silent spell, still spell, and eschew materials)? "
Nowhere in the spell description does it list any restrictions while in the magic jar. It describes how one senses his environment and the relative strength of life forces, but this has little bearing on whether spell casting is possible. A golem can be magic jarred, and the possessor can cast spells from it. An item familiar can cast spells. I see no reason why a spell can't be cast with no verbal, somatic, or material components.
