[See the start of this thread and comments here.]
Let me take your points as you’ve presented them.
(Asking the intercessions of the “dead.”)
The Church has always interpreted Hebrews 12:1 (on the basis of the faithful of the Old Testament who have died and gone before us spoken of in chapter 11) as that the many witnesses are the “dead” who are alive in Christ God. Furthermore, Revelation 8:3-4 speaks of the prayers of the saints going up as incense before the Lord. In context, it is probably best to interpret these saints as the martyrs of 6:9-11 and 7:13-17. And while it is true that the content of their prayers are not manifest (except maybe for the justice of God to be realized as pace chapter 8, if the dead who are alive in Christ are witness to our struggles in the race set before us, it seems reasonable to conclude that they pray for us as well. After all, in this life they were charged by the Apostle Paul to offer “supplications, prayers, intercessions, and thanksgivings . . .on behalf of all men, on behalf of kings and all those who are in authority, that we may lead a tranquil and quiet life in all godliness and dignity. For this is good and acceptable before God our Savior, who desires all men to be saved and to come to the full knowledge of the truth” (1 Timothy 2:1-4). On what basis would they be free of this obligation simply because they are now with God in the heavenlies? These intercessions do not in anyway negate Christ’s mediation, for these prayers are offered precisely on the basis of such mediation, as Paul goes on to say, “For there is one God and one Mediator between God and men, the Man Christ Jesus, who gave Himself a ransom for all, the testimony in due time . . .” (1 Timothy 2:4-5). We no more short circuit Christ’s mediation to us by asking the prayers of our presently alive Christians brothers and sisters, than we do asking those who’ve gone before us, absent from the body but present with the Lord (2 Corinthians 5:8), to pray for us.
More to the point, asking the intercessions of those who’ve gone before us is a practice directly testifying to the victory of Christ over death, that is to say, a faith in the Resurrection. It would seem that, despite good intentions, to forbid the invocations of the saints who’ve gone before us precisely because they have died is to deny the present reality of Christ’s victory over the last enemy. It means death is stronger than Christ. But Paul has something to say about that: Romans 8:37-39.