I have zero M3W experience, however to me it looks like you have found the fault at the burned connector. This fault could have been caused by a number of issues... the connector is undersized for the load (fuel pump) current, or more likely that for some reason the connector was a loose male to female junction, generally the female end being a loose fit..!!!
Any slack in such a connection WILL cause heat to be generated the effect of which is obvious in your picture. The burning will increase the resistance to the flow of electricity and thus drop the voltage to the load (in this case the fuel pump) causing issues perhaps intermittently at first before final failure to supply power...
That the plug is moulded is a bit of a nuisance more so if it plugs directly on to a component as opposed to being a straight through joint, were it the latter the wires leading to the two burned ends either side of the plugs could be cut out of the plug and extended to meet each other via an alternative connector...
IF the overload (too much current) had been caused by a faulty pump, then the fuse for that circuit should blow to protect the wiring, that is why I would tend to suspect a loose connection.
If you fit a new plug then chances are it will burn again as the other half of the plug will also be damaged by burning, and thus the burning process will continue and cause failure again..
If this plugs directly to a component than logically it is best replaced too.... Sure it may be possible to clean up the components connection pin and fit a new plug to the wiring which may work out OK... for a while..
Just noted that you determine the pin is clean... hmm..?
Good luck with your investigations/repair.
