I'm not sure if I told you this before or not, but I teach an early morning religion class to high school students,  every day. This school year we're studying the New Testament; last year it was the Old Testament. It was the first time I read the Old Testament cover to cover. Like I told my students, I'm learning right along with you, only a day or two ahead. That humility opened my eyes to what you talk about as the Old Testament as a Foundation. Truly it is. When I studied that foundation first, it made the New Testament so much richer. I understood and loved the Old Testament as the covenant God makes with the house of Israel, which includes not just the Jews or house of Judah but many others. He promised them some amazing blessings and gave them the Law of Moses to help them work toward them and turn them toward the Messiah. The New Testament becomes more understandable as the New Covenant when Christ comes and fulfills the law of Moses with his atonement. I think it is difficult to just pick up a book, like Habakkuk and study it independent of the whole. But it think the take home message in that book is that if we diligently seek answers form God--take our questions to him--he will make them known to us.