Grant me the power of assuring my memories are my own.

[Darklander]

In the following sentence, should one use the indicative or the superlative of word in bold?
Also would one use the accusative for both "my memories" and "my own"?
Grant me the power of assuring my memories are my own.
Da mihi potestatem pignerandi meas memorias sunt meas proprias.

 

[Ignis Umbra]

In the following sentence, should one use the indicative or the superlative of word in bold?

I'd just like to point out that the term "superlative" is used when you're talking about adjectives. "Are" is not an adjective.

You should use the infinitive, esse, because you've got an indirect statement.

Also would one use the accusative for both "my memories" and "my own"?

Yes. Esse is merely a linking verb; the subject and the predicate use the same case.

Also, I would eliminate the second meas and say the following:

Da mihi potestatem pignerandi memorias meas esse proprias.

 

[Callaina]

Pignero isn't at all the right verb here (I'm not sure how the OP came across it, but it doesn't at all mean "assure oneself of the reality of something" in this way.) Use confirmandi.

 

[Darklander]

Thank you both for your help.