78' seems high imo, you'd probably be right on the borderline. I'd think that size chiller would work. Remember your main pump will only run for about an hour per day, maybe less. Small recirculating pump won't produce much heat if you go that route. They even got ones for aquariums that the motor is outside the tank and just the impeller would be inside. I use air stones in my rez, they provide a lot of 'mixing' action plus aerate the water.
I check daily, but let pH float a little, I probably adjust pH every 2-3 days, rez change can usually go out past a week easy. If you start seeing crazy pH swings or bad water parameters you might have to change more frequently. I run hydroton, key there is to make sure its CLEAN before using it. Gotta wash all that dust off, I also soak mine(h2o pH'd to 5.6-5.8) a couple/few times before using it.
Heisenburg: I've done 'live' rez and dead/sterile rez. I didn't see a huge difference either way.
Nutes: You already know I'm a GH guy, lol. I like the floranova series, I get nice terp profiles, taste, clean burn etc...