First off, bravo for doing your research, you had many of the same impressions and ideas as me going into building my first room but I learned a lot along the way and I hope I can clear up some of those things for you here.
Ok for one thing you are not going to have enough light, secondly will most definitly need to vent your lights and not worry so much about room venting especially if you have AC...Enough fresh air will get into the room thru cracks a passive intake like that is advised assuming you exausht your room but your priority is venting those lights not the room, using aircooled hoods with a wide coverage area is key....
Trust me you will need bigger lights and better hoods that cover more area...if your going thru all this work and spending all this money your going to have to....Unless you plan to grow just like 4 small plants in this? Still your going to need to vent the lights or you will likely have problems...additionally your yield would be pretty poor with those lights and your plants wont be that happy if you grow them very big. If your growing unusually small plants your lights should be okay, me personally I like to grow the plants appropriately letting them become adults before they go to 12/12...
Next - Dont waste your time with 6" exausht and ducting go with 8"....beleive me it is nessecary for a project of this size...Ideally you want one powerfull exausht fan and the 8" inline is perfect for a room like this.....Ultimately (however not completely nessecary) you want another 8 inch for the room and one for the light so you have 2 completely indepandent cooling/ventillation systems - one for the room and one for your lights.
Regarding pushing vs pulling air - PUSHING is better - but pulling does work fine especially if you are overdoing your ventillation system and you would be with a nice 200$ 8" inline hydrofarm fan..
So if your woried about smell for the air ideall you want CARBON FILTER -> FAN -> DUCT -> LIGHT -> Light->OUT OF ROOM..... for the lights....for the room I pull so I go ROOM -> DUCTING -> FAN -> FILTER -> OUT.......I do perpetual like your planing so for the room exausht I just use a Y joint so it takes air out of each room...I do not vent my veg light...Veg Room is not a big deal really its very easy to keep in check for me especially with MH its not as hot as HPS....I dont know, vegging is just easy as hell in comparrison to flowering indoors, I did not anticipate the difference would be so much going into my first indoor flowering phase but it is much more difficult.
Dont skimp on the lights - I promise you will change your mind very soon and wish you hadnt and secondly dont skimp on your ventillation fan and dont skimp on your light hoods.
Use digital ballast they 3 times less electricity then magnetic, they dont get very hot, and they dont make a buzzing sound.....Worth every penny...I will never buy another magnetic again.
Lastly, you should consider having an actual wall between your veg and flower room instead of just poly, any light leaks can prolong flowering, hurt your yield, and cause hermies, prepare your flower side well in advance and be sure that there is no light leaking between the sides, don't wait to long to prepare your flower room like I did, I waited for about 6 weeks and than do to issues in my personal life including simply not having the money to get the flowering lights I ended up vegging plants for about 10 weeks and having 7ft monters that I had to tie in all sorts of odd configurations and having some plants go rootbound with heat issues-light leaks-every problem in the book thrown at me trying to quickly construct the flowering side and dial it in, furthermore doing construction around your plants is not the greatest thing for them, you got drywall dust and stuff flying into the air etc...... this ultimately hurt my yield tremendously.
