Who's to know who is in Heaven?

I’m confused lately, on how the church can say that all saints are in heaven. It’s difficult for me to comprehend how we here on earth can determain if someone is in heaven or not. No one has ever been there and back, it’s not reasonable for me to believe the teaching that all saints are in heaven, when we will never know until we get there ourselves. Please help… I’m really dragging myself around almost depressed about the whole issue. Thanks.

17Jesus replied, “Blessed are you, Simon son of Jonah, for this was not revealed to you by man, but by my Father in heaven. 18And I tell you that you are Peter, and on this rock I will build my church, and the gates of Hades will not overcome it. 19I will give you the keys of the kingdom of heaven; whatever you bind on earth will be bound in heaven, and whatever you loose on earth will be loosed in heaven.” -Matt 16

18"I tell you the truth, whatever you bind on earth will be bound in heaven, and whatever you loose on earth will be loosed in heaven. -Matt 18

13But when he, the Spirit of truth, comes, he will guide you into all truth. He will not speak on his own; he will speak only what he hears, and he will tell you what is yet to come. -Jn 16
The Church has the authority to canonize (declare someone to be a saint) and as the Bible said this decree is not only led by the Spirit, but it is as if Jesus Himself authorized it (“bound on earth = bound in Heaven”). A popular sign someone’s cause for canonization should be looked into is if miracles are performed when people praying to them and ask for their intercession.

If it is proven that a miracle has occurred through a dead person’s intercession, then it logically follows that the person must be in Heaven. If they were in Purgatory, or especially if they were in Hell, they would not be able to intercede with God.

Of all the billions of human beings who have died, it hardly seems unreasonable for the Church to have declared that at least a few thousand of them are in Heaven.

Based on Romans 8, even if a person is not in heaven, the Holy Spirit interceeds for you.

Also, Paul did go to heaven and back II Cor 12, as did John Revelation 4:1. So, it is possible for christians to do so today.

But the Holy Spirit is also here to lead and guide the Church into all truth - the Spirit would not intercede in the case where it would lead to Christ’s church teaching as infallible truth an untruth - namely that someone was in heaven who was really in Hell.