Z,
the $3 Realtek chip that is soldered on to motherboard obviously will not have same features / performance of audio interface.
Did you try to use Wasapi exclusive mode? (I believe you set this option is in Windows settings for onboard Realtek).
If that doesn't work, try Asio-for all.

If that doesn't cut it, there are some neat external compact solutions. My all time favorite compact interface is - Apogee ONE. Great headphone pre-amp and nice large input / volume dial. It even has a mic built in. I believe it's no longer produced, but usually available pre-owned at fair prices. There are others, even smaller ones interfaces available.