I like your handle; I think that we should question everything. However, there are quite a few reasons I question this whole Nazi secret weapons thing.

Here they are:

1. You say "right after WWII our space and defense forces and craft seemed to take a huge leap forward in progress".

Actually, most of the early work on what we now consider "modern" stuff was done in the late 1930's, including both Whittle's and Caproni's work on jet propulsion; the Brit's radar; Goddard's and Oberth's work on rockets; and, of course, Szilard's and Einstein's papers on nuclear fission. What happened was that the war channelled tons of money and effort toward the engineering development of those technologies, because all the warring nations believed that they needed them (which they did).

2. You say "What I find interesting is how right after WWII was when we started seeing the first UFO's over America."

Actually, people had been reporting UFO's for hundreds of years; it was simply that they were reported as "visions", "spirits", or "ghosts". It wasn't until the 20th century when our emerging technology led us to understand that there actually is a potential for extra-terrestrial life, that we ascribed intelligences to these same phenomena.

3. You say "the Nazi's were messing around with anti-gravitational devices where mercury was placed in some sort of container and vibrated to very high frequencies using electricity."

Yet we have no evidence of that from any of the stuff that we, the Brits, and the Soviets captured from ther Germans at the end of World War II. Now God knows that if the Germans actually had that stuff, they'd have used it, even if it were in the experimental stage; lok what they did with the "Komet" and the "Wasserfall". Those boogers were barely off the drawing board when they were rushed into production.

4. We don't have any evidence or scientific justification for mercury being used or of any anti-gravity mechanism being developed, by the Germans or anyone else.

5. By 1944, the Germans were almost completely out of the running for carrying on a war and, more importantly, having an infrastructure to get much done. Just about every single asset the Germans had was put into getting fighters into the air to knock back the 8th Air Force (which, thankfuly, failed). If they had any ships that could carry a cadre of scientists and pre-production facilities to Antarctica and maintain them for an indefinite time, there's no evidence of that, either.

6. The OP said that, "the true Operation Highjump which was to uncover the Nazi UFO Base and instead it ended in FAILURE because the person in charge went missing."

Operation Highjump, in 1947, was led by Admiral Richard Byrd, and the field commander as Captain (later Rear Admiral) Richard Cruzen. Neither of those great sailors "went missing"; Byrd died ten years later, in 1957; Cruzen retired from the Navy and died in Camp Pendleton, CA in 1970.

Most of the "evidence" I have seen on a putative secret Nazi base in Antarctica is simply erroneous information which seems to take on a life of its own on the Internet.