"In the interpreted meaning, man has power over God to snatch himself out of His hand. God only keeps something in His hand until a man decides to release it himself. That just sounds like a much weaker God to me."
Not at all, FK. It means that God, for His own reasons, respects our decisions. This doesn't mean He's weak, FK. I see where you are coming from but the consensus patrum is quite clear on this. Now Latins and the Orthodox believe the Fathers are right on this one. Clearly Protestants don't.
"I thought that Baptism was the "moment" for you all, as the sinner's prayer is for us. Since these occur at completely different times, when does the Spirit indwell?"
Baptism is part of our "initiation" into The Church. It washes away all sin, assuming there is any. Babies don't have sin, though the Latins speak of Original Sin. We believe that Baptism seals us and as it is our first reception of sacramental grace, by which grace we are able to begin to experience the process of theosis (and without which we likely can't, but, as I have said, we can't say whither the Spirit goes). It may be that for us Baptism is the "regeneration" you speak of, but I confess I don't necessarily understand how you are using the term.
We believe that when we are born there is no actually resident and indwelling Holy Spirit within us. We would say that at the point of regeneration, not baptism, the Holy Spirit literally takes up residence within us, as a "brand" of God. We are marked and identified as members of the elect for life.
At the same moment sanctification begins and the Spirit guides us through the life long process, including scriptural interpretation (I know, I know :), and prayers on our behalf. Another interesting benefit is that the Spirit prevents demons from entering into us. "There's no room at the inn." That makes watching movies like "The Exorcist" a lot easier. :)
So, when I spoke of "the moment" I meant the time that the Holy Spirit enters the body and sanctification begins.