Currently deckbuilding before starting the Innsmouth campaign.

Would blessed/cursed tokens be considered as symbols for the purpose of this card?

Yes curse/blessed would count as symbols. The card clearly delineates the options: even and odd cover all of the numeric tokens and symbol covers everything else. It's a nice way for them to future proof this card against new chaos tokens.

Aside: in this case they likely already knew about blessed/cursed (given that Jacqueline was being developed at same time as Innsmouth) so they could have enumerated all the symbols but it would take up a lot of space and left room for issues in case they added even more.