Welcome to the forum, Joann! Hopefully, you can find some answers to your questions here, but keep in mind that that the forum is open to anyone to comment, and you will get a lot of different opinions. BioLogos itself has a lot of articles and blogs available on the site that are relevent to your concerns, and express the position of Biologos itself.
You raise a lot of questions, but let me address the title question of your post, “Why does God only deal with his creation only through the Bible?”
My opinion is that this is not an accurate way to state how God deals with creation. The Bible records how God has dealt with creation in the past and gives some indication of how that looks in the present and in the future, but the Bible is not an instruction book for dealing with creation.
If you are not familar with the concept of God speaking through the two books of the Bible and creation, here is an from the site to look over:
Even that is incomplete, as God deals with creation today through the Holy Spirit, working through us as individuals and as a church, and through miraculous means.
It will take a while to absorb and integrate a lot of the information and opinions here before you can be comfortable and at peace with it. My suggestion is to continue to read and ask questions, and not be discouraged if it is a little overwhelming at first.