In case you're still wondering... In my experience, I kept Leon at bay, chose MC's ideas over Leon's, and they bonded over their shared experience rather than romance. The key part is to save Fire Station for last and there chose to "Trust Your Gut" aka search the first floor. Then, back in the house you must pick "Pull Away" (otherwise it's a bad end). You're getting a good ending if at the nest MC and Leon work together & the reinforcements arrive