Just for fun, I looked up the Vixen tank. Its rated for 115psi working pressure, with a 180psi max rating.
Doing a search on Amazon for safety air valves showed a large number.
This one,
https://www.amazon.com/Control-Devi...9587&sprefix=air+safety,aps,1062&sr=8-13&th=1
Would probably fit the bill.
Its supposed to release at 125psi +/- 3%. On the low side, that is about 121psi. Seal pressure is +/-10%, so everything should be good.
You need to see what the switch is set for, but I personally would run a 115 rated working pressure tank at about 100psi. I like a lot of safety margin. Especially if I don't remember to drain the tank all that often, and get rusty water out when I do.
Another often overlooked parameter is the cfm rating of the valve. That is how fast it can release the air at the rated pressure. The big vertical air tank that exploded had several things about it that were not right.
We bought the whole system used and did not do the checking we should have. It was working fine when we shut it down and moved it to our shop, and had been doing so for several years.
It had a safety valve, and it worked when the pressure switch failed in the on position.
When I examined the valve, it was rated at about 60cfm or so. The compressor was a large 4 cylinder 90hp unit with a 4 inch line going into the tank.
Not sure what the cfm rating of it was, but it was way the heck more than 60cfm. The poor valve did all it could do, but it could not release the air faster than the compressor could put it in, and Boom!
The valve I linked to, is rated at 116cfm, which should be way more than your pump.
You cannot get the valve pressure too close to the cutoff pressure or it will leak. They start seeping a small amount before the actual setting. The rated setting is when it goes full open.
But, if its rated at 125, and you start getting bubbles out the side at 100, send it back and make them make it good. It is stamped with both UV and NB marks, so it
should be right.