Yes, he will.

When there are two combat damage steps in combat because of a creature with first strike or double strike attacking or blocking, they act as completely separate steps with triggers resolving and players able to cast spells and activate abilities between them.

In the second combat damage step, the only creatures to assign and deal combat damage are creatures with double strike and creatures that either didn't already assign combat damage in the first combat damage step.

Yes.

You can only cast Beserk if there hasn’t yet been a combat damage step this turn. Once a combat damage step has begun, you can’t cast it. 

If there are two combat damage steps (because of first strike or double strike) or multiple combat phases in a turn (because of cards like Waves of Aggression), you must cast it before the first combat damage step of the first combat phase in the turn.

Cloudshift or Unsummon will both work, but the end of combat step is too late to do it. If you’re going to remove your creature from combat to save it from combat damage, you need to do so before combat damage is dealt.

Note that this also means the creature won’t deal any combat damage, either. Unless first/double strike is involved (so that there are two damage steps), there’s no way to have your creature deal combat damage but leave combat before receiving combat damage. Combat damage is dealt all at once.