And I admire your persistence! I've engaged in much of the same dialog and it becomes frustrating at times. Along with presenting the many Scripture passages that clearly speak of the divinity of Jesus Christ from everlasting to everlasting - it is
hardly a nebulous doctrine - we can pray that the hearts of those who resist the truth are softened and that the light of the glorious gospel is illuminated by the Holy Spirit to see the truth God made sure to teach us.
Those who formulated the verbiage of the doctrine of the Trinity relied upon the Bible almost exclusively to prove it was Divinely-revealed truth. It is why this has been something Christians have held to from the start and any and all attempts to pervert it have been shot down by Scripture which does not change. Thank you for your hard work.