1. Line in from LP/turntable.
Are you running the output from the turntable through a "phono" pre-amp and then into the line-in jack on the sound card? If not, you probably won't have a sufficient input level.
2. No
3. Far too many splits. 2500/2/20000.
If the input level is very low (and/or the recording volume is too low), you will get too many splits because the recorder interprets many sections of the music as silent gaps.
Try using the Auto volume adjustment button. Set the needle down on one of the louder sections of the LP and then press the Auto volume button. It will select an optimum volume that will give you sufficient signal strength without distortion. Some people think it's a little conservative so they like to manually bump it up a little (5%?) after it's done.
What are your settings for "Min gap between tracks", "Max gap level", and "Min track length"?
4. Correct. Had something like 75 fragmentary tracks - I left the recorder unattended for a while.
I don't know what would cause this, but maybe fixing the input level would take care of it.