Thanks. And may I congratulate you on studying the evidence you can see with your own eyes, then reasoning out the obvious truth, rather than succumbing to the easy way out. Letting conspiracy theorists (whose theories often conflict with each other) do your thinking for you is the easy way out.
Did the assassination make JFK look like a better president than he was thought to be?
Yes. John F. Kennedy was in office from Jan. 20, 1961 to Nov. 22, 1963, or just a little under three full years. He didn't have the opportunity to govern for a full term, let alone to run for a second term. Given that several months of a president's first year is consumed by various appointments (cabinet, sub-cabinet, agencies, ambassadors, White House staff, etc.), JFK didn't have much time to build a record for good or ill.
Separating the real man and his presidency from the myth that mostly liberal, Democrat journalists and biographers (to say nothing of the cottage industry of conspiracy theorists) have build up about JFK is difficult. In reality, the man's presidency ranks somewhere in the mid-level to lower third of all presidencies.
On the positive side, his rhetorical skills were among the best of post-WWII presidents. He is remembered for that one line in his inaugural address (Ask not...), as well as for his speech challenging the U.S. to put a man on the moon before the decade of the 1960's ended.
One might also say that the peaceful resolution of the Cuban Missile Crisis was also a positive accomplishment. However, his betrayal of Cuban freedom fighters at the Bay of Pigs, and his CIA's attempt to assassinate Fidel Castro led to Castro inviting the Soviets into Cuba. There would have been no missile crisis if Kennedy had handled the Cuban matter better from the start.
JFK's foreign policy was a disaster, one that very nearly led to a nuclear war between the Soviets and the U.S. Kennedy's muddled interference in the political affairs of South Vietnam, and his initial build-up of the American presence there, set the stage for Lyndon Johnson to vastly increase our military role after JFK's death.
Kennedy's first foreign policy blunder was the betrayal of the Cubans at the Bay of Pigs in April 1961, followed by imposition of a strict trade embargo on Cuba, which led to food rationing on the island in March 1962.
JFK's second big foreign policy blunder occured in August 1961 as he stood by and failed to respond while the Soviet Union built the Berlin Wall. The leader of the Soviet Union at the time, Nikita Khruschev, was a tough, cunning politician who had risen to the top of the Communist Party ranks unders Stalin. To put it bluntly, he thought he was dealing with a dumb, naive boob in JFK. So he decided to see just how far he could press the American president.
On May 29, 1962, a high-level Soviet delegation that included Marshal S. S. Biryuzov, commander of the Strategic Rocket Forces, and a high-level delegation, arrived secretly in Havana to suggest the deployment of nuclear weapons in Cuba. Castro, dealing with food rationing, a restive populace, and fear of CIA plots to kill him, jumped at the chance for Soviet assistance and protection.
October 14, 1962, the Cuban Missile Crisis begins when U.S. reconnaissance aircraft photograph Soviet construction of intermediate-range missile sites in Cuba. President Kennedy demands the withdrawal of Soviet missiles and imposes a naval blockade. Khrushchev agrees on condition that Cuba receives guarantee of non-aggression from the U.S. and Jupiter missiles aimed at the Soviet Union are removed from Turkey. Kennedy agrees. Khruschev blieves he has won a significant victory and he is right.
The Soviets maintain their influence in Cuba until the collapse of the Soviet Union. Their influence spreads to the Middle East and Africa, and Castro helps spread communism to Central and South America. Worse, Kennedy was preparing to totally cave in to Castro and the Soviets when his asassination intervened. On November 17, 1963, just days before his death, Kennedy asked French journalist Jean Daniel to tell Castro that he was ready to negotiate normal relations and drop the embargo. According to former JFK Press Secretary Pierre Salinger, "If Kennedy had lived I am confident that he would have negotiated that agreement and dropped the embargo, because he was upset with the way the Soviet Union was playing a strong role in Cuba and Latin America."
On the domestic front, modern conservatives like Rush Limbaugh enjoy pointing to Kennedy's income tax cut as a way to reinforce the benefit of tax cuts. However, that glosses over the negatives of Kennedy's domestic policy. Under Kennedy, the feds acquired intrusive new powers to snoop into the bank accounts of every American. For the first time, banks were required to report interest payments to the feds, and initial attempts were made to tax interest on bank accounts.
I'm not certain, but I believe Kennedy also signed the law that forced banks to report all withdrawals over $10,000 cash to the feds. (It's possible this latter intrusion into our privacy and personal property by the feds came later, although I don't have time to research it now.)
Hope all of this helps.