I have a suggestion. Don’t do a “Bible Study.” For you to agree to a “Bible Study” indicates, in a way, that the Bible is the only thing worthy of study, or in less extreme cases, the only thing with final authority. Which, by the way, is actually an odd notion as most, if not all Bible Studies are based on a commentary from an extra-Biblical source. Nobody, no matter how strongly they argue it, appeals to the Bible alone or even finally. In the end, they all appeal to their own acceptance of a particular translation, interpretation, etc.
If indeed you intend to procede in discussing issues of religion and theology with your Fundamentalist Bible Protestant Neighbor, it would be in your best interest to begin the discussion with an understanding that while the Bible is holy and God inspired, it is not, in fact, the only source of truth (Col. 1:24).
The practical truth of the matter is that no matter how well your neighbor knows his Bible, he only understands it as he has been instructed to. He may certainly say that the Holy Spirit has been his teacher, but the wide variety of theological traditions taught by “the Holy Spirit” should be indication enough that either the Holy Spirit is not a very effective teacher OR the Holy Spirit has some sort of a multiple personality disorder.
The reality is that he believes A, B, C because someone he trusts taught him A, B, and C. Your job is not to destroy his faith, but to challenge him to examine the reasons he believes A, B, and C. Are they consistent with historical Christianity? Did the Early Church Fathers teach A, B, and C? Why are A, B, and C “essential” and D, E, F aren’t? Who says? Why do you trust them?
And as you begin discussions with your neighbor, boost discussions with your children. Empower them. Educate them. Let them learn from your experience. Give them the information they need to answer the questions you may have to walk away to figure out.
And. . .OH MY GOODNESS, do not attend a Protestant service without your neighbor agreeing to attend Mass!