I seem to have misread the specs on Surcouf and used the wrong numbers. Oops. I'll try again.
Singapore-Bataan is 2,400 km. Surcouf's top speed was 34 km/hr. 2,400/34 ~= 71 hours, so, yes, in theory, Surcouf could make the trip in three days. But running surfaced by day would be very risky. Running submerged, Surcouf could make 19 km/hr for. a short spurt, or 9 km/hr for about 12 hours. Running submerged by day and surface by night, she would average about 22 km/hr, for a passage time of about 109 hours - 4 1/2 days. Allowing one day at each end for loading, unloading, refueling, and so forth, that means one round trip every 11 days. Two days rations delivered every 11 days would not be enough.
Yes, she could. She cannot run at top underwater speed (19 km/hr) for 12 hours straight (I suppose), but she could run 130 km at 8 km/hr, which would be over 16 hours. Most WW II submarines could stay down for over 24 hours. A few even approached 48 hours while evading attack, though much of that time would be spent sitting on the bottom or running dead slow.