Your not going to have a choice Mike. You will have to vent a 1000w light system. Having read your other posts I think I have a pretty good idea of what your doing here and it boils down to lack of commitment. Your trying to half ass this project and your finding out that it's not going to work. You bought a good light but you failed to consider that a light that big has additional factors. How much heat will it produce and what are you going to do to handle that heat? It's too hot to be left alone which you are finding out. Every inch that light is away from your plants, the cooler it will be on the plants and by a huge factor. Maybe an 1" per degree in your situation. However and this is a big however, every inch you move the light away, you reduce your available lumens to the plants. Each inch away is something like a few k lumen loss. This has to make sense to you...surely if you took your light down the hall and thought that it would feed your plants you would start to get the idea. Every inch is a life changer at this game.

Yes, you will need to vent the hood into the attic. Ideally, you will draw in the cooling air from the attic too. Practically speaking the intake and exhaust for your light will only be about 2 feet away but in the attic you need to extend those lines so that they are at other ends of the house if possible. No since in going to all the trouble of installing proper ventilation and then suck in your exhaust air too no effect.

The attic intake exhaust system is simple enough. Look on ebay for a vortex fan. 4 to 6" will be big enough for you and make sure you get all the adapters needed since you probably wont want to run 6" ducting through your ceiling. I would recommended 4" aluminum ducting with fittings to take it to 6" for the air cooled hood and finally a 4" vortex fan. 6" is also suitable for everything depending on how anal you are. Personally I find 4" to be adequate but then again I run a 600 watt light. Install the fan in your attic as detached from the rafters as possible. The fan will make noise and if your mount it right on a rafter then it will vibrate your house loose. Try and suspend it if possible. Connect to the fan your ducting that runs to the light. I think the best way is to suck the air through the hood and out to a vent in the roof. So point your fan in such a way as to suck through the hood and then push the air to another line to vent close to a whirly bird in your roof.

Your also doing aeroponics and something else I haven't seen you talk about yet is what the temp of your reservoir is. The argument is still out on how hot you can allow your reservoir to get but I can assure you that if your plants are at 90 then your res is likely way over 100 degrees. Your cooking your roots. Are they brown? If so then your res temps are too hot. You will need to figure out a way to get the plants down to around 75 or 80 at most and the water temps to around 70 at most.

Sometimes new seedlings get too tall because their stalk hasn't caught up. Make sure you aren't running the lights 24/7 and that you have a fan blowing on the plants. The fan is to help the plant grow strong not necessarily to cool the room. Even if cooling isn't an issue for you, have a fan blowing lightly on the plants to simulate wind. This will tell the plants to grow a thicker stalk.

Quit half ass'ing this project and do it right! Your on the right track, but I think you should make sure that you consider all factors on your next attempt to get things right. You don't want to keep dragging out the process of balancing out all the conditions for your plants to grow or else you wont be happy with what your plants do.