That's what wives are for. I have my wife pull the chain tight by holding the rear wheel and preasuring up on a pedal. Then I measure a foot of chain with a good steel ruler.
The Park chain checker works OK once you get the feel of it. You take the slack out and avoid too much pressure on the tool.
There is no magic amount of stretch we should tolerate. The 1/16th rule is a rule of thumb. It really depends on how much chance of cassette wear you want to take. I try to catch mine before the 1/16th.
Al