Therefore, if I say to my Heavenly Father in prayer, "Dear Lord, let my grandpa know that I love him.", then I think that God CAN do that, and that He probably will do that.
I think if your grandpa is in heaven, he already knows you love him. There's no need at all for you to tell him that from his perspective. If it makes you feel better to speak to your grandpa in heaven, go ahead. I sometimes say something to my dad, and I have every confidence somehow he already knows my heart.
But none of that is by way of asking a saint in heaven to intercede for us with God and thus try to alter our relationship with God, which is what Catholics are doing when they pray to saints and ask them to become real intermediators between themselves and God.
Which is blasphemous.
Do you think the good will of your grandpa in heaven will change God's view of you? Does God not already know how your grandpa feels? In fact, wasn't it God who gave your grandpa's love to you in the first place?
You really should read what I wrote, and quit reading beyond what I wrote.
I think there is communication in heaven among those who reside there. I think angels are alive. I think our departed brethren are alive. God is not the God of the dead, but of the living.
I think there is communication between me and the Lord.
You take it any farther than that, and you’ve left what I’ve actually said and have gone into what I haven’t said.