[lubuntu] Problem with x-server and Nvidia

I've a pc with lubuntu 14.04 but now doesn't work well as I changed some things about I use it expecially as I'm on 32'' hdmi monitor and I've changed the videocard that was damaged (but it's always nvidia).
The resolution is set to native 1920x1080 but all the fonts are too small to be read (10pt seems to be 5pt).

How can I fix the font issues?
or, better,
How can I restore the default settings of x-server?
and how can I fully remove the nvidia driver? (I'm pretty sure it's outdated and part of my problems)
Thanks in advance^^