1) This is a big problem when your new. You have to build up your content for google to find you. Upload sitemaps into Googles Webmaster's Tools. Word of mouth is the best way to start a forum. Word of mouth is getting me going right now!
2)This is the Email Providers issues. This will happen alot, and from what i've learned there's not much you can do about it.
3) Usually the Mod/Hack designer will let you know in the thread what it's compatible with. I have no idea, but I would imagine somthing designed for 3.68 and loading it into 3.7, it probably wouldn't work right.
4) Downloading from your FTP Server?