Home favorites win (outright) at a higher rate, because home teams tend to be bigger favorites...not because they're at home. For best odds of winning, it's considerably more important to be the favorite than the home team. Season to date, home teams win 67.5% of the time, favorites win 74.5% of the time, and home favorites win 77.1% of the time. ATS those same numbers are 49.9%, 50%, and 50.1%. Those ATS numbers demonstrate the efficiency of the betting market and assure us that venue is priced extremely accurately.
You could use vegasinsder.com and work backwards over time to find favorites in the 8-10 range to test your intuition on home/road splits, but I suspect you won't find any variance...just trusting the efficiency of the point spread. I don't think your strategy is necessarily a bad one, five 85% favorites will all win 44% of the time...so 1.5:1 is positive EV, I just don't think it's venue based, because I don't think there is a glaring home/road inefficiency in the market. That is intuitive to me, because step 1 in handicapping is "where is the game being played?".