He warns that those who ignore His words are building on the sand, and their house will fall

...such as the words about laying burdens on some but not others, words that He Himself did speak, according to accounts?

Yeah. That's not what's most odd, though.

Similarly it is clear that the early church rejected all forms of sexual activity outside marriage

Umm...

https://en.wikipedia.org/wiki/Adamites

...more like nudists practicing group marriage (or just abolition of marriage) and free love.

Your dreams are all in your head, unsupported by book or history (and condemned by the former).