Exsanguinate cannot affect a planeswalker at all. Exsanguinate says that each opponent "loses X life". Life loss is not damage and cannot be redirected.

Can impact tremors hit planeswalkers?

2) My opponent plays impact tremors and raise the alarm. Can he damage a planeswalker or only me? He can damage your planeswalker OR you. If a spell or ability controlled by an opponent would deal damage to you, that opponent can choose to redirect the damage to a planeswalker you control.

Do indestructible planeswalkers lose loyalty?

Planeswalkers with indestructible will still have loyalty counters removed from them as they are dealt damage. If a planeswalker with indestructible has no loyalty counters, it will still be put into its owner's graveyard, as the rule that does this doesn't destroy the planeswalker.