Check out the vacuum pump anyway
I thought all my oil in the air cleaner was coming from blowby as well, but couldn't quite believe that it would start up so easy and still leave oil in the air filter housing in qty. I simply pulled the vacuum pump fitting out of the filter housing lid and put one of my boys old white socks rubbered banded around the hose and plugged the lid hole I created and checked the white sock when I got to work. It was dripping with oil, so I knew then that my vacuum pump was pumping the oil out of the engine and into my filter housing. This is a technical procedure and requires special tools like the sock and rubber band. If you can't find them locally I can get them for you. If you just have a small amount of oil in the housing, as you say only using 1/2 a quart between oil changes, your engine must be new.