Actually, I assumed (mistakenly, now we know !) that R7 was a 33R at the first place.
So to decrease the current limit, I decided to increase the R7 value and I placed a 100R variable resistor in series with it.
The initial test value was about 100R (33R + 77R) and the current limit decreased noticeably : an inverter connected to the PSU with a 25A input load was still working properly, but no longer worked on a 50A input load (using water heating resistances, one is 250-300W, the other one 500W).
Good point, I thought, but I don't know exactly where the current limit is actually triggering, so I decided to lower R7 again but 'ON-LINE' and connected a 173Ah/12V LFP4 pack load in place of the inverter.
The charge current settled to 20-25A or so (way better than the 100A++ that occured yesterday and which led to cook the Mosfets) but increasing the 100R variable resistor did not show any variation of the ouput current to the LFP4 pack ... strangely enough
So at some point, I decided to remove the 33R resistor and left the 100R variable alone, but I must have screwed up with which way I turned the trimpot (multiturn) and the output current built up again and the MOSFETs fried ...
Unfortunately, I had forgotten to place two fuses in the sources of the Mosfets, maybe it'd have prevented the mishap (should the fuses be fast enough ...)