We can prove he gave a false prophecy from your own sources.
If Joseph Smith is a false prophet, then the Bible wasn't corrupted nor incorrectly translated. And that's the thing to consider, isn't it? Wouldn't a false prophet undermine the very thing that would prove him false?
And since he claims to be a prophet, Joseph Smith was either a true prophet or a false prophet.
Deuteronomy 18:20-22 is the test. Even your version of the King James states as much.
Copying verse 22 directly from
churchofjesuschrist.org
When a prophet speaketh in the name of the Lord, if the thing follow not, nor come to pass, that is the thing which the Lord hath not spoken, but the prophet hath spoken it presumptuously: thou shalt not be afraid of him.
So, did Joseph Smith ever speak in the name of the Lord and had it "follow not, nor come to pass" then?
Yes, several times. But it only requires one.
Let me copy and paste one such example, again, from your own website.
Doctrine & Covenants 114
Revelation given through Joseph Smith the Prophet, at Far West, Missouri, April 11, 1838.
1–2, Church positions held by those who are not faithful will be given to others.
1 Verily thus saith the Lord: It is wisdom in my servant David W. Patten, that he settle up all his business as soon as he possibly can, and make a disposition of his merchandise, that he may perform a mission unto me next spring, in company with others, even twelve including himself, to testify of my name and bear glad tidings unto all the world.
2 For verily thus saith the Lord, that inasmuch as there are those among you who deny my name, others shall be planted in their stead and receive their bishopric. Amen.
So what happened to David W. Patten. Did it "follow not, nor come to pass" as the test?
The prophecy was made on April 17, 1838. David W. Patten died in October of 1838 and never went on a mission the following spring.
This wasn't a conditional prophecy. It wasn't an unspecified time in the future. It was specific prophecy and did not come to pass.
So, according to the KJV bible you use, Joseph Smith is a false prophet.
And there are more examples, though the following website is not exhaustive on that.
mit.irr.org/failed-prophecie…
But... if Joseph Smith is a false prophet, by according to the very bible you hold to, then the Book of Mormon is also false, because he failed the test for being a prophet. In fact, the Bible says he should have been put to death.
So, if you continue to hold onto Joseph Smith, then all it proves is that you worship Joseph, not Jesus.