Your question is asking for something technically possible, in that it may be possble to "split" data in your profile, and distribute it among other profiles, but it sounds incredibly difficult to do considering what you would you gain doing this manually, as opposed to simply setting up new profiles and entering the data you wish into each new profile, and deleting the data from the other profile.
To accomplish everything you're asking for (except this splitting of the original profile data) is largely academic. The basic idea is have multiple profiles, and have multiple instances of Firefox each accessing a different profile. The way you do that is you first set up the multiple profiles, and you can do this by accessing the Profile Manager. Open your /Applications/Utilities/Terminal.app and type this at the command prompt:
/Applications/Firefox.app/Contents/MacOS/firefox-bin -profilemanager &
and the window that appears, along with information at the link provided above, will get you started on creating the extra profiles. Once these profiles are created, you can start the first instance of Firefox by clicking the Start Firefox button, and you can then launch your subsequent instances of Firefox using that same command. Again, in Terminal.app type the following:
/Applications/Firefox.app/Contents/MacOS/firefox-bin -profilemanager &
and you will see a second instance of Firefox appear in your dock. Choose the profile you wish for the second Firefox instance, and click Start Firefox. Repeat these steps (pressing the up arrow will display the last command) for as many instances of Firefox that you wish to run, or until you run out of memory.
Actually i have found solution of this issue. It seems apple didn't handled unusual cases with new Favorites tab introduced in Yosemite as far as i remember - but this is actually easy to predict, shame on you apple.
I have quite a lot pages in bookmarks (old styled, dropdown menu), and favorites tab, in favorites i have subdirectory with bitcoin exchanges. Some of those exchanges use cloudflare to prevent ddos attacks, and form time to time ask for captcha verification. It seems each time user click on URL Field in safari, favorites bookmarks appear, and safari try to download icons and maybe other meta data for each page, and then in case unusual response, it stucks safari and waste cpu on creating many threads for nothing, im not sure if it actually retry and try download again or it's strictly connected to processing downloaded metadata from page but it just make uncountable number of threads and block cpu with junk calculations. Im not exactly sure if it's caused by cloudflare check or by any other corrupted response. But finally i have moved all bitcoin exchanges subdirectory do old styled bookmarks, where obviously metadata or/and image is not being downloaded.
In case someone will need to fix it, just monitor bookmarks and safari cpu usage, and remove one by one from favorites, restart safari, and again until eliminate issue.
Best Answer
Coping ~/Library/Safari to ~/Library/SafariTechnologyPreview works for me.
On the command line, run: