Podcast merch store https://www.bonfire.com/store/the-chm-podcast-store/

Episode 19 on the Methodists https://anchor.fm/church-history-matters/episodes/19--The-Methodists-A-Partial-Conclusion-eo2pq7

Episode 15 on the history of eschatology https://anchor.fm/church-history-matters/episodes/15--History-of-Eschatology-A-Crash-Course-eo2ppl

Episode 5 on the history of church creeds https://anchor.fm/church-history-matters/episodes/5--To-Creed-or-Not-To-Creed-eo2pqb

Other resources

The Kingdom of the Cults by Walter Martin https://archive.org/details/kingdomofcults00mart (free to borrow with registration of a free account)

Website of the Seventh-day Adventist Church's official beliefs https://www.adventist.org/beliefs/