I'm a bit confused, the datasheet has different curves on the SOA for different length events, and your values are under the 100us curve so you are OK (by a factor of 20?) , oh and actually these are at 175C.
I also see you have compared your pulse energy with the avalanche energy, I had never thought to do that, and it would seem an interesting approach, given that thermal heating is more benign than avalanche heating (the latter is limited by localised hotspots and thermal runaway).
I would adapt your method however: you note a 10mJ energy pulse , so if we were to assume the transistor was already hot at the time of the transient, then the repetitive avalanche energy would be a better benchmark, which is 16mJ. So if the device can survive being hammered with 16mJ , your 10mJ transient is'nt going to bother it.
In general, You need to be a little careful about the "single pulse" data, You can't operate to the edge of this SOA once every day and call it a "single pulse" Realistically you might get 200 "single shots" before failure. I read a research paper on this recently, its a problem of thermo-mechanical cycling and short-cycle fatigue, the metallisation literally cracks up, but the stresses in the silicon actually shift the devices operating parameters (e.g. Vth, Vbr and Il ) . And they were able to measure the "premature aging" of the stressed devices vs control specimens.
OK with a bit more reading I can see the data sheet is a bit confusing, it lists 42A as the continous rating, but clearly 42A x .038ohms is only 63Watt , so the 42A is a "design to" rating , Confusingly it mentions 140A as the pulsed repetitive rating, yet the SOA shows 140A as "single pulse".
The other thing to watch (particularly when you have some of the low Ron SMD packages ) is the fuse rating of the bond wires, (typically 100-120Amps). The IRFP150N is in TO247 so fuse rating around 150A?
Gate drive: look at Td(off) , page 2 this is 3.6ohm for 90ns total off time , if you want a 5uS turnoff then the effective gate driver resistance/impedance needs to be less than 70ohms.