As far as Hyperdispensationalism goes, I haven't met many that really believe it, but I've been accused of believing it and teaching it by Cloudish people for years.
I believe that the Apostles and those saved in Acts 2-7 were accepted into the Church and will be at the marriage supper of the Lamb, but from what I can make out, the Church
Age didn't properly start until the final rejection of Christ in Acts 7 with the stoning of Stephen; in the very next chapter, the first Gentile is saved, unarguably by Grace through Faith, as per Ephesians 2:8-9 and Romans 10:9-10. Immediately following, Paul, the Apostle to the Gentiles, was saved and called in Acts 9.
Overall, I'm cautious when preaching doctrinal stuff out of the Old Testament or the Gospels, as it's easy to get young Christians confused between the Kingdoms and Gospels without an all-out study on the matter, but the entire canon of Scripture is given to us for doctrine, correction, reproof and instruction in righteousness, though perhaps not in exactly that order.
As far as the Bible school thing goes, the only on-site institute I could recommend in good conscience is Pensacola Bible Institute, and correspondence courses would include the Bible Doctrine Institute and Charity Baptist Church's course. Bro. Steve Sturgeon in Dillon, Montana has an institute which my uncle is/was attending, but he has a somewhat more heavy-handed way of running his church, so it's definitely not for everyone.
(See
this link for some information and a video that deals with apostasy in the Church and Crown College's response to the message.)