Since you have the sub, why not try all the things that you ask ?
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The group delay is better when sealed in the lowest region. With such a small room you won't be stressing the driver so distortion should not be a factor. I'd pick sealed.
my room is not long enough to produce a bass wave that lowYou mean with out reflecting off of a wall? If that's your concern, then 80 Hz is about the limit of your room.
Your room is small enough so that EQ above the sub crossover would probably be helpful.