Questions after installation - Tabs & Paths

[CompuBlog]

All front end changes should be made to the theme.. you are changing source code..

And what's wrong with that? If a theme doesn't provide the ability to make a desired change to open source free software, then a user has to be willing to dive into the guts of the system. As I explained above, when I made the background image change via the css.php file, that only worked in the admin section for whichever reason.
So what other choice do I have, if I wish to continue using that theme?
Useful answers really go a long way, as opposed to criticizing ....

It's all good and well to provide css templates, but at the same time it's not helpful to be able to make 100+ adjustments in areas which aren't totally and concisely labeled. I can't find the area where the entire blog, each and every single page including admin section, can be constrained to a width of 1100 px. I can't find the area for adding a background image which will work globally, and not just in the admin section. I can't locate the place for making at least the header narrower, in order to make what appears at the very top of the page come closer together. Yes, I can read, but apparently I'm missing something. It's really easy to criticize ... when you're the one who's already very familiar with an application.
And again, there should be nothing wrong with making hard-coded changes to php files.
I'm not creating something new, taking credit away from anyone, nor making a commercial product.

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