i=dv/dt
Sooner or later you need to measure something.
You might begin with shorting the output to ground,
with a MOSFET as switch, measuring the actual output
limited-current value; then release the FET and get
the rise time and voltage difference between two
points that appear on roughly linear portion of the
curve. That will give you a close dV/dt, you will have
a measured i, this will yield a c value from which
you should subtract jig and FET (datasheet) capacitance.
Or you desolder the cap and put it onto a C-meter,
if its markings are truly that illegible.