And then I found an even better FETs that has a Rds_on of only 9.5 mOhm (at Vsg = 10V), which is just as good as the previous one as Vsg >10 V at the output setting of 12V or more.

This FET is the Diodes DMP3013SFV. same 3.3mm x 3.3mm footprint.

And I did a measurement with 19 boards, which showed to real Rds_on to be 7.3 mOhm onaverage, because the Vsg is ~15V at the 20V setting. Also the calculated junction temperature is quite low and much more manageable now.

Results (still fixed width font anybody?):

Vfet*2    Vload    I load    P load    P fet    Tjunc    Rds on
70.5       19.47       4.87      94.77      0.343    46.4    0.0072
71.04      19.61       4.90      96.14       0.348    46.8    0.0072
70.7        19.62      4.91       96.24     0.347    46.7    0.0072
72.8       19.59      4.90      95.94     0.357    47.3    0.0074
70.6       19.64      4.91       96.43      0.347    46.7    0.0072
72.4       19.64      4.91       96.43      0.355    47.2    0.0074
71           19.66      4.92      96.63      0.349    46.8    0.0072
69.4       19.67      4.92      96.73      0.341     46.3    0.0071
72.8       19.63      4.91       96.33      0.357    47.3    0.0074
73.1        19.62      4.91       96.24      0.359    47.4    0.0075
71.4        19.61       4.90      96.14       0.350    46.9    0.0073
69.9       19.63      4.91       96.33      0.343    46.4    0.0071
72.9       19.64      4.91       96.43      0.358    47.4    0.0074
70.8       19.62      4.91       96.24      0.347    46.7    0.0072
71.3        19.64      4.91       96.43      0.350    46.9    0.0073
73.6       19.6        4.90      96.04      0.361     47.5    0.0075
72.3       19.61       4.90      96.14       0.354    47.2    0.0074
71.9        19.61       4.90      96.14       0.352    47.0    0.0073
74.7        19.64      4.91       96.43      0.367    47.9    0.0076
                                                              Average:    0.0073