Electronic – How to connect PSU to these PCB pads

I don't agree that the contact area is all that small. Copper is fairly maleable, so will deform somewhat when the screw is tightened. That will make it fit the shape of the hole for a little ways at the bottom, and the bottom of the screw at the top. Keep in mind the bottom deformation will be a bit longer than the diameter of the screw at least.

If you add up all the contact area, it should exceed the cross section area of the wire. It's probably at least twice that actually. If the connection is made properly, then it is gas-tight and should be effectively continuous copper. As long as it is equivalent to the solid copper of the wire diameter, it will dissipate no more power than the wire itself for the same length. Even if it dissipates a little more, the bar is capable of dissipating far more heat than the wire with insulation cover.

You could come from it the other way and do the math. The largest typical house currents are 30 A, which requires #10 cable legally, at least here in the US. A copper bar like that should be able to get rid of 1 W of heat per junction point without any temperature rise that matters. The resistance to dissipate 1 W at 30 A is 1.1 mΩ. That would be a surprisingly high resistance for such a joint with a #10 cable.

If you really want to know, test it. Get a bar, some copper cable, and test the resistance. It will be so low that you will need to do 4-wire measurement at decent current like a few Amps, but it should be doable.

The datasheet describes device as very well noise immune one with ratiometric (to power supply) output from DC to 400Hz. So to read DC "ratio" well, try use 2+2+2=6 wire "drive" "sense" cable for 2 devices. At DC you are affected by ohmic, galvanic, thermoelectic forces, but not the radio.

-- Drive --->--*-----+----------------------------+
-- Sense ---<--/     |                            |
                     |                            |
-- Sense ---<----Device (of DC half bridge type),Device--->---Sense--
                     |                            |
-- Sense ---<--\     |                            |
-- Ground --<--*-----+----------------------------+

All 3 sense wires should meet ratiometric input of ADC, say top goes to positive reference input of ADC, middle into positive input, bottom sense goes into 2 pins: negative reference (of balanced input) and negative pin of input.

Edit: Other thought. If there is movement on flexible cable, think about "triboelectricity". If cable friction, hit, vibration is an issue, then read specs about correct impedance of load. If this is high impedance, then add differential "line drivers" with current loop output and match a type of ADC to be "current ADC". Or better add small ADCs on board itself.