Install/deinstall Woes

I'm trying to replace an install of Reflection with (firstly) Blue Sky and now Delegate.

I installed mem_template and copied over the Blue Sky folders as instructed. For some reason this was enough to activate Blue Sky even without going through the Import process in mem_templates. The changeover was incomplete, probably because the section, page, form and styles were clashing. I lost all of my graphics (well they weren't referenced by Blue Sky)

Nonetheless there was enough Blue Sky functionality to demonstrate the advantages in leaving Reflections behind, but we felt that Delegate would be closer to our needs, so I downloaded that, copied it to the directories and imported it through mem_templates. I was comforted that each theme has its own directory under _templates, but disconcerted by there not being a similar one for site-design. I can't be sure that importing the later theme didn't corrupt the earlier.

In any case after spending a good deal of time removing pages and forms as per the instructions and renaming the sections and then the articles to conform to the theme I discover the following problems:
1. The logo image is missing and the default site name doesn't appear instead
2. The slider doesn't appear, even with some articles assigned to featured-article status
3. No articles appear on the home page, but the sidebar lists recent articles
4. The nav bar doesn't contain all sections
5. The Theme Variables tab contains none of the variables listed in the Help pages
6. The Widget Variables tab contains none of the variables listed in the Help page

Asssuming I somehow botched things when first installing Blue Sky, I attempted to reinstall Delegate via mem_templates, which changed nothing. I then deleted all of the directories containing Blue Sky or Delegate stuff. I deleted all plugins except those I knew not to be associated with those themes and then copied across Delegate again, reinstalling via mem_templates. This changed nothing.

Can you help me with these points:
1. Is it possible to have one or more themes loaded into the directory structure and to switch between them by using mem_templates?
2. In such a scenario how can one tell which theme is active?
3. With things as wrong as they are described above what is the appropriate troubleshooting technique here, particularly to recover the theme and widget variables?
4. At this stage I'm looking at a total reinstall of txp and theme, followed by uploading of articles. Is this the best course of action or are there easier/better alternatives?

In my own defence I should say that I have long experience with xoops, which provides a dynamic system for swapping themes that is painless, and I assumed that txp would behave the same. Wrong.

Lee