Odour control need depends.. Its best to be prepared, but its funny when it is/isn't needed sometimes.. Be careful though, sometimes odour just ends up where you don't expect it to be, and you definately want to be the one who finds any odour.. Roof exhaust is pretty ideal though, and some older houses do have that stink pipe that goes right down to the basement.. With roof exhaust though you can't underestimate the back-pressure created by the climb.. You need alot more cfm..
I would say at least 2 inlines the size of whatever piping its going into, maybe more. I would probably want to go ahead and install some sort of odor control though. I'm thinking of an ozone generator. A buddy i know just got one for $180.00, cleared out the stench from a fridge full of rotten meat in 1 hour. smelled like right after a thunderstorm. Sounds worth it to me!!lol
I'm not saying you want 110F at all, I just mentioned that since its an interesting fact tied to notion that humidity helps combat higher temps, but that increased water loss with gas exchange trumps the increased reaction rates I mentioned..
I found in my room, in the winter time, i could control the humidity great by adjusting the thermostat on the heater. a five degree adjustment higher drops the Relative Humidity 10-15% in about 5 minutes. Summer time is a different story.......im going to need a dehumidfier!!!
Passive intake is fine.. You can increase your intake rate by increasing your exhaust rate.. How many cfm is that fan rated for, and how long/straight is any ducting if its attached to any?
Hot air rises, so you probably aren't sucking it back in from below, but it is possible that you're exhausting cool air as soon as you suck it in (which leaves more hot air in the room), if I'm picturing things right.. It really is best to have intake low on the opposite side of the room from the exhaust.. On that note, a circulating fan near that intake, or an active intake might help get more of that cool air deeper into the room.. Not exactly proper HVAC protocol, but worth checking..
Also, if you do end up adding active intake, ducting it to the opposite side of the room would get the air over there, so its not pulled right up to the exhaust..