High end oil coolers are rated much higher than 100 psi. A 60 row Earl's cooler I have is said to be tested for leaks at 175 psi and burst checked at 350 psi
https://www.holley.com/products/plumbing_an_fittings_and_hose/cooling_systems/oil_and_transmission_coolers/narrow/parts/26016ERL
Also worth noting that the pump I used showed no signs of being compromised by the cooler. The interior of the pump looked fantastic and the bores in the pump body to support the gerotor shafts were nice and tight.
http://forums.pelicanparts.com/porsche-911-used-parts-sale-wanted/653744-sc-oil-pump.html
for whatever that's worth..............
The 930 pump flows a bunch more oil than the SC pump does. The 930 pump has a huge scavenge section by comparison. This pic shows various pumps and the one at the bottom is a 964 pump which is similar in dimensions to the 930 pump. You can see the left side of it (the scavenge side) is much longer than the other pumps. The longer the pump, the longer the are the rotors inside and the more it can pump.
From top of picture to bottom:
1. pre-'69 (aluminum)
2. '69-'76 (3 rib magnesium)
3. '76-'77 (4 rib magnesium 2.7L bypass mod)
missing in this sequence is the 78-83 SC 3.0L aluminum 4 rib pump
4. '83-'89 (aluminum 4 rib with built in strainer) Note that some of the 3.0L engines would have a so-called 3.2 Carrera pump since there were some SC engines produced with the later engine case with no removable sump plate)
5. 89-98 (964, 993 made of magnesium or aluminum depending on year)
Here's a picture of the real deal 930 pump
Targalid you should read this nice thread started about the pressure relief valves. It gives good insight as to where they are in the system and what their cracking pressures are
http://forums.pelicanparts.com/911-engine-rebuilding-forum/712724-ultimate-oil-pressure-relief-valve-thread.html
The external t-stat bypass is completely separate from the two internal engine oil pressure reliefs and the two oil paths are independent in terms of pressure. The external t-stat is fed by the scavenge side of the oil pump. The scavenge side of the pump does just that. It scavenges oil from the bottom of the engine case and returns it to the oil tank so it can be fed back into the engine. It just so happens that the t-stat and oil cooler are in that scavenge route. But that pressure within the scavenged oil route has no dependence on the oil pressure within the engine. Think about it and I believe you'll see what I mean. When the pump sucks oil out of the engine case, it immediately sends it to external hose/piping which takes the internal engine pressure relief valves out of the picture so to speak.
So in other words the internal engine oil pressure and scavenge route path oil pressure are completely independent, pressure-wise, despite being driven by the same component- the oil pump. The oil pump is sometimes referred to as a tandem oil pump and that's because it's two separate pumps in one body.
Also, your statement that oil does not flow through the t-stat and cooler until 186°F is not entirely correct. When cold, the t-stat is open on the side feeding the oil cooler and closed on the return side. So what that means is there is a "dead end" pile of oil coming out of the t-stat, thru the cooler and back to the t-stat. That pile of oil is seeing oil pressure from the scavenge side of the oil pump pushing oil back into the tank, even though the pump is being relieved by the somewhat low pressure free flow of oil going back into the tank. What's important here is the pressure against that dead end is greatest when the oil is cold and that's when the bypass in the t-stat is a very good thing to have.
My belief of the 100psi cracking pressure for the t-stat came from these threads
http://forums.pelicanparts.com/porsche-911-technical-forum/700478-large-leak-front-oil-cooler.html#post6947597
http://forums.pelicanparts.com/porsche-911-technical-forum/607698-oil-pressure-filter.html#post6013141
Here's a comment from pro engine builder Mike Bruns (used to be with JB Racing in Florida but not any longer, I believe, as it's no longer in his signature and he's not posted since late 2014) about the pressure in the scavenge circuit
http://forums.pelicanparts.com/911-engine-rebuilding-forum/695694-creating-crankcase-vacuum.html#post6936128