PokerTracker

Does it seems right?

sum( if[tourney_hand_player_statistics.val_equity>0
AND char_length(lookup_actions_f.action) = 0, (tourney_hand_player_statistics.val_equity * tourney_hand_summary.amt_pot), 0] )

divided by

sum( if[tourney_hand_player_statistics.val_equity>0 AND (char_length(lookup_actions_f.action) = 0),(tourney_hand_summary.amt_pot), 0] )

*100

I would like to complain about my unlucky sessions more accurately, it's not that important

As far as I can see that should give you the average proportion of the pot you could expect to win when all-in preflop. I'm not sure what you mean by "weighted" though, as this seems to be a straight average.