First things first - relax 
I did option 3 with Flo and she had Nobivac at 9 weeks and 11 weeks as the vet wanted her to settle for a week before 1st vacc.
I did option 5 with Remy. 1st vacc Eurican with breeder then 2nd Nobivac at 10 weeks and 3rd Nobivac at 12 weeks with vet. Although Nobivac and Eurican are compatible vets advice was that Nobivac wouldn't guarantee complete protection unless their product was full administered. This kind of backs up your statement "vet's belief that the combination of two brands of vaccinations is less effective".
Option 2 sounds like the best idea to me
Which ever way you go Saffi will be just fine.
I did option 3 with Flo and she had Nobivac at 9 weeks and 11 weeks as the vet wanted her to settle for a week before 1st vacc.
I did option 5 with Remy. 1st vacc Eurican with breeder then 2nd Nobivac at 10 weeks and 3rd Nobivac at 12 weeks with vet. Although Nobivac and Eurican are compatible vets advice was that Nobivac wouldn't guarantee complete protection unless their product was full administered. This kind of backs up your statement "vet's belief that the combination of two brands of vaccinations is less effective".
Option 2 sounds like the best idea to me
Which ever way you go Saffi will be just fine.