when I post on my blog how do I create XML feed so that the post also appears on my home page and also a link from my DP sig
I believe that would involve cURL. You would set a script on your server to check your own profile page for content updates, and then fetch it via cURL and use in whatever way you want it.
I have some free time and i could do this script for you, just explain me better what you want, i don't understand very well what you exactly want. This is what i understood : you want a script which grabs your last post from your blog and post the blog post link in your DP profile page and in your sig. Is this what you want?