You earn points based on the number of participants (size of the field). If 20 people enter:
1st - 20 points + 5 bonus points for winning
2nd - 19 pts
3rd - 18 pts
.......
19th - 2 pts
Last - 1 pt
Ties are averaged over the number of ties. If three people tie at spots 10, 11, and 12, then they each get (11+10+9)/3 = 10 points - this is where the 1/2 points come from.
For the season standings, your lowest tournament score is dropped so only the top 9 of 10 scores count for the segment. 3 segments of 10 tourneys each - playoff points are awarded the same way as the tourney points for the top 10 spots only:
1st in Segment - 10 playoff points
2nd - 9 playoff points
.....
10th - 1 playoff pt
Ties handled the same way - averaging the points for the tied finishing positions. Playoff points are added to your playoff performance totals to declare the season champion.
Hope that makes sense.