Where we profoundly disagree is that you seem to think any religious expression in a government setting is an 'establishment of religion'. I don't think you can make a case for that. There is simply no way that a two-word phrase in the Pledge or a generic prayer in any government setting or an art object of anything is an 'establishment of religion'.
The intent of the Constitution was that government could not use its powers to require you to believe or not believe anything respective of religion, nor can it require you or forbid you to exercise your religious faith in any way that does not break the law or violate the rights of others. Now if you can show me how 'under God' in the Pledge takes anything away from you or requires you to express belief in anything or do anything or forbids you the right to do anything, I'll listen.
If you cannot do that, then it must be concluded that your adversion to those two words arises not from any violation of your inalienable rights, but rather arises from your own personal prejudice to which you are also entitled. It just doesn't give you the right to dictate a policy contrary to the majority will..