I meant to put the resistor before the 1,5KE-13CA, but leave the 1,5KE-13CA protecting the rest of the circuit. The resistor would be in series with the top left wire in the circuit.
That will stop the 1,5KE-13CA from protecting anything else in the car, but will provide better protection for the 5 V regulator.
Load dump, if it happens, can continue for some time. It can also be repeated if there is a bad connection that is connecting and disconnecting as things move. The specification sheet for the 1,5KE-13CA shows that it can absorb 2 kW for 10 ms, or 5 W continuously. Well a load dump is around 1 kW and will decay to zero over 100 - 500 ms, and that is a lot of energy to absorb, and I think that it is above what the 1,5KE-13CA can manage, but the graph doesn't extend beyond 10 ms.
Suppressors like that are excellent for absorbing inductive spikes that are of short duration, but load dump goes on much longer.
I once repaired a car where the engine to body earth wire had broken, but had not fallen away, so it kept making and breaking the connection. The car finally stopped when the protection diode in the engine management computer shorted out, and the 5A fuse feeding it blew. It made me realise that load dump protection is very hard to do, and adding resistance means that a supressor has a lot less current to absorb.