I would finish the flight with 51hrs PIC 101hrs TT
midiman would finish the flight with still 50hrs PIC but 101hrs TT
If you think that being SLF time in the back of a 737 should count towards your total time, no objections here. You both would also be one hour older. But that's not the point.
The point is you cannot count any of that 737 pax time, or time as "second pair of eyes" in a SEP towards any experience requirement for license issue/renewal. In the end, for CPL/ATPL etc. it's not the "total time" that's required by the regulations, but the time acting as PIC, SPIC, PICUS, P/UT and so forth.