Hello and thank you for using just answer!
If you PROPERLY drain the engine oil on this car and also change the filter the the oil capacity is right at 6.5 quarts. That drain cap on the oil filter housing is just as you stated a drain for the filter housing only, they put that in place to allow you to drain the filter before removing it, I personally do no do that and I do exactly as you do with draining the filter just by unscrewing the entire thing. Be sure that you have the car on level ground and that you check the fluid level within 30 seconds of shutting it down. If you drained it right then your oil level should be right on.