That torque reference might be for a castle nut. See what they supply you with. If it's one of those crushed nuts- I wouldn't go past what Ford says for fear of stripping it. The metal doesn't look as hard as what large castle nuts were made out of. 290 is VW axle nut crazy, you'll need to sit a truck on top of a 10' long rigid pipe to remove it.
When I think of castle nut I think of cotter pin style, and what was supplied are not castle nuts. The nut is self locking via three equal spaced crimps on rather indentation in the smooth collar at the top of the nut. I would call it a crushed nut. The 290 value came from the Advance auto website on this product, I just found some info that came with the half shaft and it indicates to follow the vehicle manufacturer torque specification, now that makes sense. So, by following vehicle manufacturer spec you are also following the part manufacturer spec, perfect. Haynes sez 173 ft lbs, so that is it, unless someone tells me that Haynes is not following Ford. (
As far as the discrepancy between Ford and parts suppliers when it comes to the trans filter- that's up to you. Personally, I'd rather have the rubber gasket, you'll find RTV on it from the factory because that's how Ford does it. I use Permatex Indian Head Gasket Tack to glue the gasket down to the pan, then put the pan on, but you likely already know that since you seem to know enough about parts. I'm a bit surprised you asked this question anyway [scratch]