Use the search function for "JFK lives" discussions, I've lost count of how many we've had but the last was not even 6 months ago.
Short term: Terry Sanford replaces LBJ on the ticket. JFK wins a landslide only about 20-30 EV smaller than LBJ's over either Rocky or Goldwater. All the stalled New Frontier legislation goes through because of the lopsided 2-1 liberal majorities in the 89th (1965-7) Congress. You will see Medicaid, not Medicare because JFK will not be able to outmaneuver the AMA like Johnson did IOTL.
Space was a means to an end, essentially a photo-op to beat the Soviets. Both JFK and RFK held this view.
Vietnam: see NSAM 273. The OTL strategy, which was keep the war Vietnamized (Nixon's OTL Vietnamization was merely a return to the Kennedy policy) remains, while arms shipments of frontline equipment to SVN take top priority. All or most of the advisers are withdrawn by '65.
Cold War: attempt at Nixon/Kissinger detente.
For the rest, as I said, use Search.