Probably a clamped power class, and any way you slice it that'll be a tough score to beat.
No, because most orgs are doing clamped power classes outright or just have something written in the rules that they can reclassify amps as needed if the issue arises.
Cool. Hope you had fun.
I would not rely on sweeps. Really you can't even be certain about low power testing, but test every tone up to about 65hz and see what happens (disable your subsonic filter or turn it all the way up first). You may see more than one peak, for example, wherever your box is tuned and wherever your vehicle wants to peak. You may have several tones around one of these peaks that meter very close to the same. IF you wanted to really optimize you would do best to try to get your box to peak wherever the vehicle peaks but that will probably not do so hot for music.
If you have mutltiple close peaks test again at full power (giving ample time to recharge battery and cool down coils and amp(s). You may also notice that the peak frequency if it's unclear will be a little better up or down one cycle depending on the weather/day. Pay attention to things like temperature and humidity and see if you can determine a pattern here.
My peak is 42-44 depending on the day and has been with every box and wall variation I've done in my Jeep. Definitely no rule that only high frequencies will get loud, though I don't think 30hz range is going to really do you any favors with cabin gain in any vehicle. If you cared you might could try to rig up some swappable ports for competing or even add a second identical port to the one you have now and plug that at shows.