As a general rule, don't use tools to tighten fittings - they should only need to be hand tight. That goes double for anything you are tightening into acrylic (like a block or res) - if you overtighten you'll crack the acrylic.
The EK STC fittings are designed such that you can use a hex key inserted up inside the barb but if you use that to tighten the fitting be very careful not to over-tighten - it would be very easy to do so with an allen key. The locking collar doesn't need to compress the tube much to press it onto the barb and make it tight.
When you say "0.5 to 0.1" do you mean a full 0.5 bar or do you mean half way between two dashes (which on mine would be about 0.0125 bar). If it's just dropped half way between two dashes after serveral hours, then I'd be fine with that on my loop.
I think the table in the leak tester manual is for "re-certifying" if you've disassembled something. So the listed product should be able to hold the quoted pressure for at least 15 minutes after re-assembly. For testing a whole loop you're not checking that it holds a specific pressure, only that your loop is basically airtight. So, I'd say don't worry too much about the actual charging pressure.
I aim for just into the green section (maybe about 0.55-0.575 bar?); leave it for about half an hour or so and check it's not moved. Then you can do a wet leak test - like
@Haz123 says, make sure you
only power the pump after filling and ideally run it over night (so 8-10 hours minimum). I put kitchen towel in to hopefully make any leak more obvious.
If I remember correctly, the EK temperature sensor has a 3-position connector, with the wires in the two outer ones? And I'm guessing the header on your motherboard just has two pins next to each other? I ended up swaping the cables into a 2 position connector because I had some around, but if there is space next to the header on your motherboard to take the EK connector you should be able just move one wire to the centre position to make it work. If you push a tiny screwdriver or needle into the exposed metal half way up the connector, you can free the clip and then carefully pull one wire with the crimped on terminal out (don't tug too much, incase you pull the wire out of the crimp). Then just push it back into the centre position until it clicks back in.