Also fully tightening the screw, so that the diaphram doesn't move, might stop or slow down the leak. If it's not closing it'll see a little less pressure right..
The pressure check function of the screw is a side effect, not it's primary function. Pretty sure you knew that, but others maybe not. No you can't use this inplace of the fuel pressure tests
Yep replace it. It's already out.
It doesn't really look big enough to smooth out injector pulses, but I'm sure the toyota engineers knew what they were doing. Just looks so tiny
And if you really want to try the locktight to seal the screw, like incase it's the cap in the diaphram instead of the rubber. Go for it, screw will either be long enough or you can press on the bottom side of the diaphram. Looks like a metal cap there to me.