If this were my car, I would replace the coolant reservoir with a reservoir from a junkyard from a vehicle that uses a standard, old-fashioned, radiator cap. I would then go to NAPA and get a radiator cap with a low pressure specification.

My objective is be to reduce the coolant system pressure.

In the old days, if your cooling system sprang a minor leak, and everything else was fine with your engine, you could limp-by by "releasing" the radiator cap, which essentially caused your cooling system to run at ambient pressure.

Your coolant system is working under pressure for two reasons: 1) to raise the boiling point of the coolant and 2) to prevent cavitation at the water pump.

Assuming your engine is in basically good shape, and you are not driving the car like a race car, I would not worry about issue 2). And, assuming you have a good mix of antifreeze in your engine I would not worry too much about 1).