1. Prime95 is not suited for B1=110M (a.k.a. "the 55 digit level"). This is because the max. overall bounds for Prime95 is 4290M, but with B2=100*B1 (which is smaller than optimal), B2=11000M...
Using max. bounds, a Prime95 curve only counts as ~1/3 standard curve, IIRC.
For B1 > 43M, yo ushould definitely use gmp-ecm. Before, I'm not sure which one is faster, as stage1 is faster with Prime95, whereas stage2 is faster for gmp-ecm.

2. Output will be in "results.txt" - either when a factor is found or when all curves have been done.

3. A factor can be found after the completion of each curve (after each stage of each curve, to be specific). ECM is similar to P-1 factoring. The big difference is that ECM tests (with different sigma values) search for different group orders.
As a massive (and mathematically wrong, but descriptive) oversimplification, just imagine ECM as "P-sigma factoring".

4. Searching for increasing digit counts of factors is AFAIK proven to be most efficient. So, the 50 digit level (B1=43M) should be done next.