You forgot about BA SEA-LHR-TLV or DL/KL SEA-AMS-TLV. The cheapest option may be to piece together two tickets with Norwegian, SEA-LGW and LGW-TLV.
Also, think about the total distance. In nautical miles, that would be:
FRA 6,035 nm
AMS 6,036 nm
LHR 6,111 nm
YYZ 6,821 nm
EWR 7,033 nm
SFO 7,039 nm
LAX 7,410 nm
A transfer in Europe will make the total distance much shorter.