(1) There's no direct way to do this.
(2) eValid is a stateful product so its internal state is critical. It is likely that if you start a script in the middle without having done the first part then your eValid browser state will be such that the latter part will NOT work correctly.
Starting from the beginning each time, from a known state that is reproducible, maximizes the chance that that state of the browser at the time you reach you breakpoint.
(3) You could easily split the long script into two parts so that:
is equivalent to the original. This makes runing to the Breakpoint easier to do, at least.
(4) You could just run Part2.evs and see what happens. If it works, great! But we're not hopeful...
eValid Support Team