I would not depend on FB for load data, it might be in error in something less obvious than your #5b OAL.
Your #4 is right to start, current production HP38 is The Same as W231, not just "close enough". Look on the Hodgdon site, load data is identical down to the last tenth of a grain, fps, and CUP. There is no difference except the label. Old books will show different loads because Winchester was distributing their own powder and had slightly different canister grade specifications. No more. I have watched a dealer open a 50 lb keg labeled HP38 but the packing slip buried in the powder said 231.
I would normally recommend the Hodgdon www or print data but they are sticking to numbers derived from the Hornady 230 grain flat point at a lot shorter OAL than roundnose. That is a safety factor, deeper seating, lighter loads.
I have not loaded any large amount of 230 gr .45 ACP with more than 5.2 gr of HP38 because it easily makes Major power factor at that, velocities in the 750 fps range, more ore less depending on the gun. I am not out for factory equivalent.