And did it all come to pass? Were the predictions specific enough to legitimately prove his gift?
Nothing, no, no, what gift?
Next!
A prophet isn’t a soothsayer, you’re confusing two different concepts; a prophet can be a soothsayer, but that’s neither the only definition nor its, uhm, defining aspect in a religious context. From m-w:
1: one who utters divinely inspired revelations: as
xxxxa, often capitalized : the writer of one of the prophetic books of the Bible
xxxxb, capitalized : one regarded by a group of followers as the final authoritative revealer of God’s will <Muhammad, the Prophet of Allah>
2: one gifted with more than ordinary spiritual and moral insight; especially : an inspired poet
3: one who foretells future events : predictor
4: an effective or leading spokesman for a cause, doctrine, or group
5: Christian Science
xxxxa, a spiritual seer
xxxxb, disappearance of material sense before the conscious facts of spiritual Truth
Mohammed was type 1b, you’re thinking of the 3rd definition. He was the “follow the paths of the Lord!” type, not the “there shall be war” type.
He foretold that, one day, everyone would be able to spell. He got that one wrong.
The noun is prophecy (pl. prophecies) with a long E, pronounced: PRAH - feh - see
The verb is prophesy with a long I, pronounced: PRAH - feh - seye
The verb gets conjugated:
I prophesy
You prophesy
He/She/It prophesies
It’s the last form that confuses people as they think the word is ‘prophesize’, and back-fills it into the non-existent verb “to prophecize” which then leads to the non-existent 'he prophecizes."
It’s “to prophesy,” and “he prophesies.”
I’m a grammatical prophet.
insert alternate pronunciation thread here…i.e that isn’t the way much of the English speaking world says the word (PROH not PRAH and stress on the last two syllables if any)
proh as in rhyming with doe or go?
not quite, shorter than those…don’t really know how to explain without using another ambiguous example.
PROH as in prod. But it’s pointless trying to explain this to most Americans as they hear/say “prod” as “PRAHd”. 
GQ answered by Nava – Prophet meaning one who transmits authoritative revelations from God. Muhammad is attributed the characteristics of definitions 1b, 2 and 4.
In Judeo/Christian/Islamic contexts proper acts of a prohet in transmitting revelations can include lawgiving, denouncing of unrighteous behaviors (with or without smiting), proclamation of what God wants done, and ISTM the least instances of canonical prophecy are those involving specific verifiable foretelling.