Re Room Gain, I don't think that the room "cares" whether the bass is coming from a ported sub or a sealed sub, or a bass drum or stringed bass, or whatever. The room "supports" the low frequencies it will, no matter the source. The reason room gain is less pronounced for ported subs is simply because the output of the ported sub drops very quickly below port tune (about twice as quick as a sealed sub would be below that same frequency), so there's less output for the room to support.
Suppose you have a ported sub tuned at 20 Hz, and a sealed sub capable of the same output as the ported sub at 20 Hz. Suppose that your room gives you 6 dB of gain at 22 Hz and 8 dB of gain at 17 Hz. Then play a 22 Hz tone at 90 dB anechoic. The output of both subs will be increased by 6 dB, to 96 dB.
Now play a tone at 17 Hz, with the same signal strength. The ported sub will probably be down 8 dB (playing at 82 dB anechoic) while the sealed sub will probably be down 3 dB (playing at 87 dB anechoic). Both subs still get an 8 dB boost from the room at 17 Hz. The in-room response for the ported sub will be 90 dB (82 anechoic + 8 room gain), while the in-room response for the sealed sub will be 95 dB (87 anechoic + 8 room gain).
Just wanted to clarify that, since there seems to be some confusion. And, as always, this is as I understand it.