It si telling that you hanging your "separation" hat on the private letter of a lone signatory - and a letter that was written DECADES after the Declaration and and 15 YEARS after the Constitution.What's tellling is your attempt to dismiss Jefferson and Madison as "lone signatories". Jefferson wrote his words as President (indeed clearing the letter with the Attorney General) and Madison is recognized as the primary author of the Constitution.Such evidence would not even get a ham sandwich indicted.
And your other quote is interesting. What year was it? It looks like another afterthought of a lone signaory. (All sorts of politicians try to rewrite history to make themselves and their ideas look better - looks like these two you quote attempted to do a little ex post facto revision)
Indeed the occasional nods they made to religion were more likely to have been political in nature.
-Eric