That DTM4425 have good RDS value but is terrible at disipating heat, it makes pretty clear why all my Phanteks hubs have died.
For what I see, and if I'm not misunderstanding anything, seems our best bets without breaking the 1 poound barrier, are the FQP27P06 and the IRF4905PBF, or AOI403 if we can lose some power for the best RDS value.
If price is not a problem, seems like SUP90P06-09L-E3 is a wonderful part for this project and could handle cooling for a small nuclear plant. Also , the older version of this ones can be found in China much cheaper than standard mouser /digikey / ... prices, I think only difference is not leadfree pins.
PS: I totally forgot about what you said about the potentiometers. Yeah, I see I need no more watt handling on the trimmer now, dunno why I was convinced I needed more in the past...