1) The captcha is temporary until one has a certain # of posts...to deter spammers n solicitors n such; everyone endures it early on.
2) I had the same issue, be sure you aren't using a capital letter if it requires lower case and vice versa; be sure spelling is correct, and be sure it is the correct wording...lol. It can be stubborn, I know.
3) Little can be done about topical trajectory...LOL. Admin/Mods will clean up the thread at some points to remove clutter, but with free will and proud hearts there is no fully controlling which way a thread will go. Best you can do is utilize the inefficient quoting system to highlight specific contributions you are replying to.
4) Welcome to the world of Christian forum, haha..the surest place to find stubborn hearts, fierce resistance and generally opinionated conversation...LOL! But in the end most of it is meant well and a lot of good support/encouragement is given.