Hyphen Versus Parentheses
They have different uses. Parentheses add explanatory information to a sentence (this removes the need to make a whole new sentence) that is related to the subject matter. Em dashes show a change in thought — changing the subject mid-sentence was something Kant loved to do — that will eventually return to the original though.
In your examples, I would use commas.
Please, as far as I am concerned, do feel free and safe to text me anytime you'd like.
Please remember that I voluntarily admitted to you that I had been indirect, and thus less than honest, in asking you the question in the first place.
Do note that I changed the word order in the first example.