1.9 divided by (Sine 45*) = 2.69?
I'm guessing that 'stroke' should be measured in line with the pushrod...

Just noticed you mentioned a paper gasket, something which Citroen never used, just like the paper gaskets folk now fit to carburettor bases.
I'd leave that off, but fill the base of the pump and the spacer 'hollow' with grease.

Hi Ken,

I've just mounted the old pump & old gasket (indeed without paper gasket), first greasing the area of the lever. After a few seconds starting : squirting like hell !!

So ...... yes it is working, we have a fuel supply ....... but I do not have a hard conclusion about the failure of the new pump ; wether it has been the (incorrect ?)thickness of the gasket or just not enough capacity / output pressure to overcome the difference in height level between tank and carburettor.
So the only thing missing is - like you said - to measure the output pressure - unluckily I do not have the equipment to do this measurement

... I hate it when I can not point my finger at the cause of a problem, the new pump thus remains suspicious ...