A catch can might do you some good with respect to the gunk in the line.
Do you do a lot of in town or short trips? In cold damp weather condensation will build up, if you don't drive long enough to fully heat the engine. At least once a week you should get it out on the interstate and let it cruse at speed for 10 miles or so. That will heat the oil in the pan and evaporate water that has built up.
You don't say your odometer reading but 1,500 per quart, while not optimal, is not terrible. I don't think GM will do anything at this point but you might want to get it "on the books".
That was the good news. The bad news (as I'm sure you already know) is that it your oil consumption won't get better. Keep your eye on your oil level and use high quality oil.
Lots of luck!
I forgot to mention that in cold weather that gunk can freeze. If that happens the PCV system may cause the block to pressurize (due to blow-by pressure). If that happens the crankshaft seals can blow out and suddenly you will have no oil and a huge repair bill.
Last edited by spook; 12-02-2018 at 04:32 PM.
Reason: Adding a thought.