AprilSteel . . . . . . . .
Your closeup photo of your unit, precluded picking out fine foil path detail / routing.
Refer to this closeup and the app note at the side.
Since you have minumized the R factor of the R-C time constant already, just work with halving
the C value and make a test timeout . If you grossly err, hopefully using the resistance of the vari pot will let you correct enough to trim into your new shorter activation period.. If not , keep playing with slightly decreasing C value.
You probably will not have cap measuring capability or surface mount stock, so use a conventional leaded ceramic cap . . . or mini poly.
CIRCUITRY REFERENCES :
Edit . . . .I pulled up from browser memory and thought that I was adding onto page 2 end . . .but I now see that more was added earlier on . . .after I saw my post showing up much later.
73s de Edd