As far squads, rangers had (and still do) the same sized squads as the other 'conventional' units. They just had les squads. And secondly, for this mission, yes you are an OSS opperative, but you are attached to a Ranger unit! which means that you have to stay and take orders from the unit in question. So at least for this misson you should be with a squad, and the squads should be actual 'full-squad-strength'!
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"Victory at any Price!"
SS-Panzergrenadier