Hi,
I'll take a simple guess on the first problem. Are you using the ENTER key when typing the text in a paragraph? The ENTER key actually signifies NEW PARAGRAPH and would probably look double-spaced return on a preview.
When typing a paragraph, allow the text editor to automatically wrap the text while you are typing. There's a nice set of functions to left, center, right, and block justify the text in a paragraph (just above Font on the editor). You can mouse-select the text and apply those too.
On the other portion of the post, all of those formatting items have use; it's just a question of FORM vs. FUNCTION.
Danno