God does know the future. It's kind of complicated.

God knows the future, based on my understanding of the Bible, it's both because He exists in the future and He also makes choices to determine future events.
Now, this next concept is a little bit less obvious to find in the Bible. I might even be overthinking it. But, there is a God who controls EVERYTHING and KNOWS all things and is ALL POWERFUL.
Can He create beings who can freely make choices?
And I think that is some of what the whole reason we exist is all about. I think God chose to make beings who can choose. God chose to make our original parents in such a way that their choice to turn from Him was magnified in all of their offspring, yet God did not re-create new beings, otherwise, He would be creating evil, which He cannot do and He is not the originator of evil. That is why when we see the tragic results of cruelty towards young "innocent" babies and children, we should not blame God, but rather 1. The person who made the choice to be cruel and 2. The devastating consequences of living in a world that has rejected God and does not receive His protection against evil, but instead God is allowing evil to be seen for how awful evil is. When He judges, it will be seen by the angels and all those redeemed as righteous judgment. For those being judged in the future, this will be the just anger of what is good coming against what is evil, and that is actually terrifying, if you are on the side of evil.
People should not doubt the goodness of God or His love for people because He showed great kindness towards people by sending Jesus to take the wrath of God in our place. Because He is the God-man He could die once a physical death to remove from us the eternal death and separation from God that is the sentence we are under.
As far as "the elders who are sinning" goes, the context would be those sins that are contradictory to the lifestyle of one who is leading the church of God. There are lists in the Bible that are very restrictive simply because the life of a leader should be exemplary.
It is true that all sin is sin, and all sin, including believers.
It is not true that every pastor or pastor's wife commits adultery, or is guilty of extortion or crimes of any nature. It would be wrong to lump everyone together and imply that since all sin, leaders cannot live exemplary lives.
To put it in clearer terms: when choosing a marriage partner it is better to choose one who lives by moral standards and cares about others than to marry someone who has demonstrated cruelty to others and does not care about any moral code. That doesn't mean people can't change and do bad, I'm just trying to make the point that even though we all sin, there are different degrees of sin, seen in believers as well as unbelievers.
Sorry about your wife.
Oh, I didn't finish my thought, so although God knows the future, because He made us with a true ability to choose, although within the constraints of what He allows and the opportunities He gives, the choices to receive or reject Him are ours and happen.
So, God knows the future but we make choices that He foreknows but doesn't force.
That is my opinion and I have to state it like that because it's not completely clear in the Bible and there are theologians who have wrestled with this far more than I and it seems rarely do any come to the exact same conclusions with each other.
I'm going to be late for church if I don't stop writing!!!