Kuskro, I've followed your advices and now my T68 works very well! In particular I've noticed a lot of improvements unistalling Google Services and moving the biggest apps on SD Card.
I'd like to advice only 2 more improvements:
1-Full!screen doesn't work properly, at least on my device. It often doesn't restore the system bar and it's no possible to refresh the page by the left botton when the full screen is on. I've found a small app in the forum which works very good and it's possible to refresh the page as well.
It's possible to download it
here
2-Calibre and
Calibre Companion are a good couple. With Calibre Companion is possible not only to syncronize ebooks by wifi and cloud, but it's possible to syncronize marks of read ebooks between Calibre and C. Campanion and sorting in C. Companion the ebooks according to the last read ebooks as well. I think it's a good way to replace the Onyx Launcher
How to configure Calibre