IMO you have left out one main filter that i have always used, pick your races now my type of race may not be yours but i only bet in races that are OPEN and higher.

No 3yo only races
No Fillies & Mares races
No Restricted of any kind

It has to be Open, Quality, Group races even the country events have open races.

This may not be everyones idea of race filtering but it has worked or me.