I need help with saddle setback and I'm starting to chase my tail. For some background info, I'm 6'4", 200ish lbs with a 36" inseam and a long torso. I ride a 61 Specialized Roubaix Pro that I started riding in March. I had a bike fit on my old bike and the fitter told me I needed a 102mm setback on a Power Saddle. When I first got my bike, I had a CG-R seat post that has a 25mm setback and I couldn't get to 102mm setback on a Power saddle. I tried a 0 setback seat post and at 102mm, it felt uncomfortable with a lot of pressure on my hands. I tried changing stem length, it didn't work. I did a balance test, I felt the most comfortable with the saddle setback at 120mm. I set my saddle at that point and did 25-mile ride on three consecutive days and I thought I was golden. I had an event that was 103 miles ride and after 20 miles, my bum was KILLING ME and I suffered the rest of the ride. I'm not sure what to do now.

Here are my questions:
1. If I changed the saddle to a longer saddle than a Power (240mm), would that change saddle setback or would it be roughly the same? As an example, if I got a 270mm saddle, would that add or subtract from my setback?
2. I'm now confused about what setback I need on my seat post. At 0 setback, the 102mm would work, 120mm, an 18mm setback would work, 120+ the CG-R seat post would work.
3. Should I stick to my balance test or KOPS, or what my bike fitter told me I needed on my old bike or should I just eyeball it?
4. I got in three rides before the 103-mile ride with that saddle setback at 120mm, should I keep it at 120mm and see if I get used to it?
5. Should I burn my Power saddle in a volcano and get a longer-nose saddle?