You sound like the eternal pessimist!
There is nothing in a theme that will break Moodle. You can get locked out but you can also get back in and change a theme.
First trick that I use is set your Moodle site to 'Allow theme change by URL'. You can do this by going to the 'Theme settings' page found here...
Administration > Site Administration > Appearance > Themes > Theme settings
This will enable you to use another theme by adding ?theme=standard should the one you be using turn its evil eye on you!
The Admin layout in Moodle is set as a 2 columns page, with the side block contents is on the left and the main contents is on the right. This is so that the major part of the page is free to view tables that contain vast amounts of students names and details and grades and all sorts of data that needs to scroll to the right, simply because we read for Left to Right.
If you have a theme, where all the blocks are on the right, you can end up in an Admin layout page and have all the blocks on your right hand sidd and still scroll, but is alwasy looks so cluttered like that.
You can have blocks on the right throughout the theme if you want to. You can do this in any theme that has three columns by just dragging the left hand blocks over to the right hand side of the page, and setting them on that page to be always positioned on right.
This ability to move blocks, has always been the case in Moodle, so you can have a site that has blocks on the right and the majority of Text and images on the left.
This is the first thing I found out about Moodle back in 2008/9 when I first came across this software. Blocks can be moved on every page providing that Admin has set that to be allowed.
Each block has its own page setting and its own site setting, so that it knows where to be it these are set. The thing is that people can't be bothered setting pages up. It takes time like populating a database. Building a database can be a piece of cake, populating it, however, can take forever...
TRY THIS AS A TEST...
First of all without changing the layout of the Magazine theme, go to the Frontpage and turn on editing and start to move the blocks from the left over to the right. Then when they are all in place go to each individual block and set it to always be on the Right and make sure it is set this way Site wide as well as on the page you are working on (Frontpage) at the time you are editing that block.
After doing that go to a course page and do the same. Please remember to save you settings.
Let me know how you get on.
Mary