Well.. let's see if we can help you help yourself first - then see what is left that you need help with...
First - and not in your list - is your gallery should be upgraded. 1.5.44 is the latest - including several security related fixes since 1.5.16 that it appears you are running.
Upgrades are not difficult unless you have modified CPG code. Staying within the 1.5.x family should mean your plugins are fine.
Upgrade info: http://forum.coppermine-gallery.net/index.php/topic,78867.0.html
1: you said you fixed
2: look at the CPG config page under 'Album List View'. You will see 'The content of main page' specified as something like 'breadcrumb/catlist/alblist/random,6/lastup,3'... You should be able to adjust this for most of what you asked for at least... See the help associated with that selection.
3. I don't see 'Stella' listed in the gallery itself - but do see it other places on the site...
Would need to know who to change it to in some cases (name/email used to report any copyright issues as example...) - other places can just be deleted... I'd expect these should be simple changes, but mostly outside of CPG.
4. Not familiar with the plugin specifically (know of it) - but without the plugin - the config option (under 'Thumbnail view') of 'Go directly from thumbnail to full-sized image' would bypass any intermediate images.
If intermediate images don't exist - the original would also be displayed (unless it has been replaced by intermediate via admin tools).
5.I believe there is a plugin to do this - try searching the forum.
6. This would likely be a change in your theme - shouldn't be a difficult change.
7. Looks like you already have turned off the ability to leave comments - which removes most of the visible support.
Only references I saw with a quick look are 'Last Comments' in menu, and '10,074 files in 422 albums and 68 categories with 0 comments viewed 647,852 times' on home gallery page... Are there other items you need to remove too?
8. In config under 'Thumbnail Settings' you can adjust the size of thumbnails (and what aspect to base it on...)
Admin tools allow for rebuilding thumbnails...
The size of album thumbnails is set under 'Album List View' settings.
9. A theme change here - don't expect that would be too difficult.
See what the above can get you through... If you are still interested in help - I will send you a PM with my contact info... I will have limited availability this coming week- more time next week.