You calibrate against a reference standard. The purpose is to set up the device so it provides standardized results. You tune a device to a particular application. The purpose is to provide improved discrimination at some region of interest.
(1) An offer is open-ended; it puts something in front of another person leaving that person free to accept or reject the offer.
E.g. "We offer several afternoon activities for you to consider." "Please offer a cold drink to our guests."
(2) A suggestion is a soft way of presenting an idea for something to happen; you may hear people say, "Never mind, it ...