Indent width via width attribute in the <p> tag. Set it to <p width="0"> for the equivalent of CSS text-indent: 0; any other integer for a custom indent.
Space between paragraphs is done via a blank <p> with an inside.
It will be incredibly tedious to add spacing by hand, even via a simple search/replace, unless you're just using one occasionally for a section divider, so I advise if you want lines between all your paragraphs to set it via an external CSS stylesheet which KindleGen (and probably Mobipocket Creator) will automatically "translate" during the conversion to Mobi format.