You might try using the default Tournament Scoring and Overall Scoring formulas, and ignoring points entirely.

The default Tournament Scoring formula is "log((n + 1) / r)" and the default Overall Scoring formula is "(1-exp(-average(scores))) * 100". This ends up giving a "ranking" of players, and it really isn't dependent on how many tournaments a player participates in, but rather how they rank relative to the number of players.

You could modify the Tournament Scoring formula to add a slight bump for making the final table. For example, "log((n + 1) / r) * if(finalTable, 1.1, 1)" would add 10% of whatever the player scored for that tournament if the player made the final table.

Just a suggestion.