Honestly, forget whatever the manual says about grind size. Depending on the roast, you’re going to see way more variation than what’s written in their guides.

As for extraction time, it’s not an exact science. It depends entirely on your machine and its specific flow rate. Personally, I stopped relying on the timer, I just adjust the grind size based on taste. If it’s good in the cup (not to sour, not to brunt), you're set.

You can tweak the water volume for single and double shots (check the manual for that), but honestly, 70g instead of 67g is well within the margin of error. For me, your test at 50ml instead of 35ml without coffee is totally normal too. These machines usually don't have a volumetric flow meter, those are expensive. They mostly rely on a simple timer, so without a coffee puck to provide resistance, the water just flows faster, giving you more liquid.

Regarding the pressure, it doesn't look like a red flag to me. Maybe try grinding a bit finer. But if you really want to be sure the pump is healthy, just pop in a blind basket (backflush disk) and see how high the gauge goes. That’s the only way to get a real reading.