For me it’s the opposite, dreary weather typically lifts my mood a little when I’m sad. It’s like the whole environment joins me in my gloominess, and my feelings don’t feel as out of place.

That is true, but it is still not known if Jesus was referring to the whole Torah, parts of it, or to some other law we don’t consider. We do not know his stance to other jewish sects at the time, other than his dislike of pharisees. My point is that it’s all just pick and choose, there is no single voice or historic certainty or any of the sort

The Old Testament that is used today has not yet been decided upon until quite some time after the probable span of time in which Matthew was written, we actually do not know for certain what texts are referred to here.

It is true that the Bible does not have a single message, and contradicts itself often, so Christians necessarily pick and choose, even if they don’t want to admit it.