However FAR 25 is not an operating regulation -- rather it defines certification standards to Boeing, Embraer, Airbus, etc. Describes minimum flight paths for flight test engineers who are compiling data for AFM.
Yes, but part 121, which is what I've linked, are operating regulations...
Edit you use the lowest of the weights to meet the most restrictive limits as certified and approved by the POI
the minimum missed approach is designed for OEI---if you can't meet that limit you are overweight for the operation and are therefore operating illegally---at least with TERPS the assumption of OEI-missed approach must be built in to the procedure design
