But Paul isn’t talking about “all men” in Ephesians 4:6. The context clearly restricts the “all”, just as it restricts “aionios” elsewhere. Paul writes:
“I, therefore, the prisoner of the Lord, beseech you [dear “saints who are at Ephesus”] to walk worthy of the calling with which you were called … endeavouring to keep the unity of the Spirit in the bond of peace. There is one body [of Christ] and one Spirit [life], just as you [dear saints] were called in one hope of your calling; one Lord, one faith, one baptism; one God and Father of all, who is above all, and through all, and in you [dear saints] all.”
He continues his epistle while remaining in the context of believers and their ministry. There is no reason to assume he is talking to or about everyone who has ever lived in one random sentence amidst a single admonishment. So in this context, Paul must be talking about a present reality for believers: they are one holy and catholic church, with one Lord, one faith, and one baptism, regardless of the different denominational modes. He is encouraging them to “keep the unity of the Spirit in the bond of peace” to avoid schisms (a strong pattern in Paul’s work). Why should this unity be preserved? Because Yahweh is the Father of all (who have one Lord, one faith and one baptism); this says nothing of nonbelievers, although it can be argued from elsewhere. So yeah, I do agree that Yahweh is the Father of everyone – it is truly one of my stronger convictions (hence my moniker) but I don’t think Paul is saying this here. If universalism is true (and I suspect it might be), I look forward to our first big reunion too
Our God is certainly a loving Father, brother! (This much I know). I wish you the very best in your searching!