Sounds like a few problems;

Forum search will help with the "no memory" problem ... ie nothing left on the root. Which in turn helps with installing apps, updating etc.

Unstable may be due to limit file space on the root for various temporary settings to be stored. Seen a few mentions of flashing not "cleaning" out old file structures. You may need to ssh into the phone and remove /var/apt contents and some other files. /usr/share/themes for example hogs a lot of root space. Just leave the default on there. Mplayer eats up space on the root too.

In sum ... forum search is your friend and patients can make a good product great. Btw its not a phone, internet tablet that can make phone calls, treat it more like a computer and it will seem more usable.

Used my phone for months now without a single issue not caused by my own fiddling. I love the phone, but then I have had practice on a Zaurus SL-C1000 and i-Mate JasJar.