About the supposed "law" against contact with ET's.
It doesn't exist. 14 CFR Section 1211 (an administrative regulation, not a law or statute), was repealed in 1991 and has not been replaced. It was passed in 1969 for the obvious purpose of preventing contamination from whatever might return with the Apollo astronauts. I invite anyone to read the actual text that you provided, and come to their own conclusions about its intent. In fact, even the UFO site link you provided that discussed the reg and its nefarious prohibitions admitted that it would take a "stretch" for the regulation to be interpreted as banning any contact with ET's. In fact, the tale of 14 CFR 1211 is so bogus that it actually earned its own entry on scopes.com, home of urban legend debunking.
http://www.snopes2.com/legal/et.htm
As far as Ike and his dentist, I'll shorten things by assuming that there was a cover-up, and that he did something besides going to the dentist. But nothing in that link provides any evidence other than the fact that he wasn't where he was supposed to be as support for the claim that he was viewing space aliens. That's just terrible deductive reasoning by whomever is making that claim.
Let's say I get invited to a function I really don't want to attend, and give the excuse that "I have to work". Someone checks up on me, and I'm not at work. From that, they deduce that I must have been viewing the bodies of space aliens. See the problem? The only link to aliens in the story you provided was from some loony guy whom even that site did not believe.
Just because a certain theory fits the facts doesn't mean its correct, because there may well be plenty of alternative theories that also fit those limited facts.
As for the rest of the stuff, I already spent too much time ferreting out these first two things you listed, and twice accidentally deleted my almost complete response. I'll just reiterate the general comments I made before about the reliability of the conclusions drawn by both self-described experts and lay persons regarding ET's, and leave someone else to address the details.