No you can't. Not unless your amplifier offers the facility of such bass management.
That would depend on whether the combination of room and subwoofer would need it and this can only be confirmed by measurement. FWIW, part of my reasoning for suggesting the XXLS-400 was the likelyhood of your small(ish) room giving strong room gain below your lowest room mode which will be about 32Hz. With the sealed box this will manifest in flat response below this point leaving only the area between 32Hz and your chosen crossover (50Hz ish I would guess) to sort out with a bit of positional tuning. Not really a big ask. The naturally flat response of the Monolith by comparison could be boosted beyond flat into giving ever increasing amounts of bass low down, potentially requiring plugging the port as a minimum, or EQ as a worst case.
Yes and no. You can't cure the rooms
problems with EQ, but you can effect a flat (in the frequency domain) and short (in the time domain) response at your preferred listening position
If you look at the first two graphs in the first post of this utterly fascinating thread
, the SMS-1 EQ device has been used to flatten the response (at least below 50Hz - I ran out of filters) in the frequency domain and as a result has reduced the length of the audible ringing. The decay time hasn't been shortened as the decay gradient hasn't altered, but as the sound is starting from less of an SPL peak, it takes less time to decay into the nominal noise floor at about 45dB (SPL).
It stands to reason, that if you EQ every single frequency possible at the listening position, then you'll likely make the response worse elsewhere in the room. That's why treatment is superior; It benefits the entire listening room, it's just that EQ is a lot less visually offensive in the average living room.