Hi hesser and welcome:
You should try better media (Verbatim or Taiyo Yuden). Although your unit should be able to handle -R format, you might have better luck with +R with the bitset changed to DVD-ROM format (I know you said to keep it simple but it’s relatively easy to do).
What speed are you burning at? Here’s an excellent tutorial on burning speed.
I looked at your combo unit on Amazon and the reviews were very poor. so these changes may help.
Nero CD Speed can help with the bitsetting and has many other uses.