I have found that my most controversial posts are the ones that are received the best, oddly enough. I think that's true simply because I'm honestly speaking my mind. I do try to be tactful, but I still think honesty is the best policy, even though that's trite.
As for the spelling/grammar errors, copy and paste your post into a Word document and use their spell check, etc. to check for anything you miss. I do a Wordpress blog and have found that even if I find the mistakes later, I can go in and correct them and update the post to reflect the changes. I also "preview" my post and read it all the way through to check for this kind of stuff and to rethink my content. I don't catch things 100%, but it helps eliminate a lot of things I might otherwise miss.
In the beginning of my blog, I made a step-by-step list to make sure I did all the steps necessary to make sure everything was posting correctly. It really helped alleviate my fears.
Read the book, "Quitter." It's by a Christian blogger, but his stuff is really relevant for all of us trying to blog and write. I think it will help reduce your fears.
Hope these suggestions are helpful. Happy Blogging!