You are understanding right. I missed the dehumidifier. That rejects all its heat into the room so you need to add that capacity + 25% more for the compressor's heat of compression. So a 6000 btu dehumidifier would add 7500 btu an hour into the room. Keep in mind it isn't running all the time but you still need to account for it. That's probably why yours wasn't keeping up.I'm really liking the carnival. I hit a cut with my PM x UD male to see how that mixes in. That was my last cut of carnival, but I have 4 more seeds.
On the AC, for the space I have overkill. As for wattage, I have 6 quantum boards, which I have built in pairs that I believe run 260 Watts, so 2660 for lights, 6583 for my space so 9243 combined if I'm understanding you correctly. Still pretty close. I was running a separate dehumi in there for a while because my AC unit wasn't pulling the humidity out when it was cool enough to not run. I've figured that problem out, but that was generating a lot more heat it was having to deal with. Now that it's had time to rest and chill down it seems ok. I know I'm stepping it up if I end up taking to replace it.