How does Arcbond interact with Saving Grace?
The result of this combo will be three damage events: the original shock, plus the two Arcbond triggers. The first deals 2 damage to the 3/3, the second deals 2 damage to your opponent and each creature you don't control and 10 damage to the 3/3, and the third deals 10 damage to each creature and player. After that point the 3/3 will be dead, so there will be no more Arcbond triggers.

The reason it works that way is because Arcbond's effect is a triggered ability, which means that each time it triggers, there is time in between for other events to occur, and Saving Grace's effect creates a replacement effect, which modifies the damage events in place.

The exact sequence of events is as follows:


Your opponent casts Shock targeting your 2/2 creature.
In response, you cast Arcbond targeting that creature. Arcbond resolves, and creates a delayed triggered ability that will apply for the rest of the turn.
Still in response to shock, you also cast Saving Grace. Saving Grace resolves, and its triggered ability triggers. The creature is now a 3/6. That triggered ability also resolves, and creates a replacement effect that will redirect damage for the rest of the turn.
Shock resolves and would deal 2 damage to the 2/2, but Saving Grace's replacement effect modifies it. Instead it deals 2 damage to the 3/6. Arcbond's delayed triggered ability triggers.
Arcbond's triggered ability resolves. This would deal 2 damage to each other creature and each player, but Saving Grace's replacement effect modifies it. Instead, it deals 2 damage to your opponent and each creature you don't control, and 10 damage to the original creature. Arcbond's delayed triggered ability triggers again.
At this point, the creature has taken 12 damage and it has only 6 toughness, so it dies as a state-based action. The Saving Grace is also put into your graveyard as a state-based action.
Arcbond's ability resolves again, and deals 10 damage to each creature and each player.