For 2, I've never seen any spam here ever. Maybe the forms are designed with hidden fields that catch all those spambots like XRummer that read CAPTCHAs better than humans.
For 3, well the thing with importing settings is K-Meleon ...
It wouldn't hurt to have installation instructions, which should be like:
1) Copy your bookmarks file to another folder.
2) Write down what your settings are.
3) Copy everything in your plugins directory
4) Make sure you have written down all the saved passwords you had K-Meleon memorize
5) Uninstall old version
6) Install new version
7) Copy your backup of the bookmarks to where your new bookmarks file is and overwrite.
8) Go through your notes and re-update all settings
for 2.) We remove spam. I am one of the censors
Info is in threads about lost profiles and such. There might be info in wiki?
Yes, it would be fine if an English speaking person makes summaries for wiki.
1.) ok. Copy the whole profile to a save location (btw. There is even an extension for automatic backups).
2.) Prefs are in Profile's prefs.js.
3.) ok. Plus most are autodetected as long as they on Your PC in an plugins dir or... Here are some examples:
C:\Programme\Windows Media Player\npdrmv2.dll
Opera, safari... all except IE use the same plugins.
Plugins in K-Meleon's plugins dir are preferred if two plugins can handle the same mimeType
4.)pwds are in *.s (* = random number) - copy and paste inside the new *.s after You created it by setting a pwd. You also need the 3 *.db files if masterpass is set.
5.& 6: ) Or give each new install a new name such as K-Meleon1.5.2...
After You crated a new empty profile for its use
7.) or set bookmarks plugin to use bookmarks.html at an old location
I use one in K-Meleon1.1.4. That keeps them synchronized.
8.) Prefs.js are reusable within the same major version.
Compatible: 1.0 - 1.0.x same version.
Compatible: 1.1 - 1.1.x same version.
Compatible: 1.5 - 1.5.X same version.
In case of a version change You can edit the Prefs.js but the user interface is faster and safer. The recent versions have a compatibility macro that can be activated. And it auto updates old settings. So You do a backup (just in case) and try whether the updater works for You. It normally does.