Okay! Thanks for that information. I'll give a shot at addressing some of your questions:
I can't find that option at all in Joomla! 1.0.13, so I am a bit at a loss as to how to answer you. Under the "Site -> Global Configuration -> Server" screen of the Joomla! admin section, you do have the ability to determine how new files permissions are handled, and those should be set to "Dont CHMOD new files/dirs (use server defaults):. They should already be properly set for DreamHost (644 for files and 755 for dirs) by virtue of DreamHost's umask settings and the installation process. Leave this alone.
That is not an "error" it is a "warning" that is much more relevant to users in a particular situation (see [this DH wiki article on DH configuration and Joomla!). There is additional information in this DH wiki article on Magic_quotes, including how to change the setting if that warning message bothers you. Generally speaking, you should have no problem, security or otherwise, with the default DH setting for this. WHeter or not you elect to change that setting is up to you, but you cannot doi ti via .htaccess at any rate (see the previously referenced links).
That question has already been answered in another post in this thread. .htaccess.text is just a "pre-prepared" .htaccess file that you can use "as is" if you need to implement the SEF urls section of the Global Configuration. You only need an .htaccess file if you are going to place some directives into it. I don't know the details of the reference that you saw elsewhere, but I suspect the context in which you were reading had to do with certain PHP directives not working with PHP-CGI. ,htaccess files are read by the server when serving a page and many things can be done with directives in an .htaccess file, though those things differ whether you are running PHP as an apache module (mod_php) or as PHP-CGI (as it is by default on DreamHost.) Google can help you find out more about all of that, or it is a subject for another thread.
All these choices are matter of personal choice, though the control of what errors are displayed is an important part of any "security through obscurity" concept. Frankly, once your site is deployed, it should be error free, and I have no problem with DreamHost's default setting in these areas. You can, of course, change then as you see fit by installing your own version of PHP or using a copy of DreamHost's PHP and your own php.ini file (see the wiki for instruction on each of these optioins).
I've never found the need for any additional back-up software other than the traditional *nix tools - sftp, rsync, wget, tar, etc. You can always dump/export you database via phpMyAdmin or other tools, and back up the code for your site via the tools I've already mentioned. If you find Joomla Pack to be useful, I say "go for it". You can also use automated back-up scripts (see the wiki) if you want to use traditional back-up methods with reduced interactivity.
Whew! Hopefully, that has answered some of your questions. In the future, please consider giving each question (at least those that are unrelated) its own thread, as it makes it a lot easier to address them "one at a time" and makes it easier for others searching for similar answers to identify a relevant post, eh?