Hi there... a bit of info.
the AS Air flight will depart and Arrive in T6 at LAX. Your flight coming and going from LAX from Brisbane will be in T1 (have done it before and have an itinerary currently for next month in front of me flights to Sydney and Melbourne leave from TBIT). Clearing customs on your way INTO LAX will mean landing at T1 and taking a shuttle bus to TBIT to then clear customs. From there you can easily walk (or take the bus, I always walk) to T6 to fly to SEA. Coming home you will simply need to walk from T1 to T6. For the way into LAX I would leave AT LEAST 3 hours (my last trip was a breeze however with GE). Layover of an hour in SEA assuming no delays is fine.

PS there are earlier flights to connect from SEA to ANC than 1900.....not sure why that one was selected?