Cotterpin bb conversion

I'm working on getting a 1960s Torpado up and running and have removed the
cranks and bottom brack spindle but can't get the fixed cup off (it's got
three notches, not opposing flat faces, and I don't have the proper diameter
lockring and hammering with a screwdriver is just damaging my screwdriver).
I'm thinking that I could just leave the fixed cup on an get a new bottom
bracket for the other side and put on newer square-taper cranks. So I've got
few questions:

1. If I dremel or otherwise get a good hold on the cup to put the frame in
the bench vice, which way is the fixed cup threaded?

2. If I go for a new square-taper spindle, is there a formula for
determining a proper spindle length? Current spindle is 134mm end-to-end,
42mm edge-of-cone-to-end driveside, 32mm non-driveside. The bearings look
to be the same size (1/4"?) as other bottom brackets so I'm assuming I can
use the fixed cup that's well fixed in there.

Thanks in advance,

Seng