There is no establishment clause
The Constitution, Supreme Court, and the entire body of US law and jurisprudence disagree with you.
because people forget the rest of the sentance after the comma
No, they don't. Well, at least the people who realize that it's unconstitutional to force a religion on anyone didn't forget it.
nor prohibit the FREE EXERCISE therof. Which basically nullifies the first part of the sentance.
No it doesn't. The first part refers to, and forbids, a religion being established, endorsed, required, or mandated by the governing body of the US. The second part refers to, and gurantees, the right of the individual to exercise whatever religion they wish, without fear of preemption, reprisal, or discrimination by the government. That right ends with the individual at any point where it would infringe upon the rights of free exercise, or the prohibition against the establishment of a religion.
The original intent was to neither endorse or prohibit
No, the intent was to bth endores and prohibit. To endorse the free exercise of any religion by a citizen, and to prohibit the establishment of a mandatory or state sposored religion.
People need to READ their constitution
Anyone can read it, and still fail to understand it's meaning. The fault is in reading it not for what it say's, but for what parts you can cherry pick to support whatever agenda you intend to advance, rather than what the founders intended.
There's no excuse, it's freely available on the Internet and many organizations will give you a printed one free.
I'd go one step further and advocate that an entire year of schooling be devoted exclusively to the constitution, it's meaning, it's intent as established by legal precedent, and it's effects on law and civil society. Hopefully with the effect that everybody will be able recognize cranks like yourself for what they are, people with an agenda that favour a single group of people to the exclusion of all others.