Live in Peace Versus Live at Peace

"Live in peace" means undisturbed whereas "live at peace" means not to be in conflict.

• My parents advised me to live at peace with our neighbors.
• After such a busy and hectic life, I should like to retire to a remote spot in the country, where I could live in peace.
• In those quiet and pleasant surroundings, he felt at peace with all the world.

"At peace" is sometimes used as a euphemism for dead. For example, he's at peace (= dead). But the words said on someone's funeral are "rest in peace."

Reference: "English Prepositional Idioms'' by Fredrick T. Wood.

Bonus: On Versus Onto

"On" and "onto" are both used to point out movement towards a position:

• The hare jumped onto the sofa.
• The hare jumped on the sofa.

However, there is a difference between these two prepositions. "Onto" being more specific indicates that the movement was started from an external point. 
"We wandered onto the ground" means that our roaming was started from somewhere off the ground whereas "we wandered on the ground" means that the roaming was started somewhere on the ground.

Prepositions with Point (Verb)

The usual prepositions are "at" and "to." When "point" is used transitively, it normally takes "at" (e.g. point a gun at someone); when it is used intransitively, both "at" and "to" are idiomatic, according to the idea expressed. The difference is as follows:

Where some visible marker or object is concerned, "point to" means "indicate by pointing", whereas "point at" means "point in the direction of."

"Look at this," he said, pointing to a blood stain on the carpet.

"And now," said the guide, as he pointed to a small ivory casket, "we come to the most interesting exhibit of all."

One of the boys was pointing at someone in the garden.

it is rude to point at people.

But when more direction is in question, without reference to any particular object, "to" is used (e.g. point to the east, the north etc.). Direction may also be indicated by "towards."

"Courage I," he said, and pointed toward the land, "This mounting wave will roll us shoreward soon."

"Point to" express indication, not only of visible and material things, but also of non-material. ("All the evidence collected so far points to robbery as the motive of the crime.")