Good advice so far. To add to whats been said, 3-2-1 is for beef ribs or pork spare ribs, 2-2-1 is for pork baby backs. Both of those times are figuring a smoker running 225-250. The times are also an estimate. Maybe try 2.5-1.5-.5. Personally I don't like to foil pork ribs so I run them the whole time on the grate no foiling. For beef ribs I feel that they benefit from the braising stage that they get in the foil.
As for the 225 being to high for ribs, that's about as low as you can go and get them done safely. I actually smoke mine at 325°, and they take about 3 hours total time (naked no foiling).
Pellet smokers are notorious for temp swings. The heat ramps up then drops then ramps up then drops, same thing happens with most electric smokers. Another thing that pellet smokers can have happen is that the fan can dry things out faster. You really need to get a good remote therm to test the accuracy of your smokers settings. Its very possible that you are running higher than what it says. My friend has the same smoker you have and he is 25°-35° degrees above what the setting is.
For therms look at the Maveric 732 or 733, or the iGrill2. I own the iGrill2 and the Mav732. the iGrill is spot on accurate the Mav732 probes are a couple degrees off which is just fine. 5-10 degrees off is okay for pit probes but not for food probes.
Here's a good read for testing temp probes and a calculator for adjusting for altitude and barometric pressure.
http://www.smokingmeatforums.com/t/...is-212-f-an-accurate-measure-of-boiling-water
As for the black bones. Does your rub contain sugar? Sugars burn easily and I leave them out of my rubs. My go to for ribs is salt, pepper, onion, garlic (AKA SPOG) and chipotle powder. I don't sauce my ribs but my boys like there's sauced so they get sauce for the last 30 minutes or so and the sauce contains enough sugar.
Another issue could be that you aren't getting a clean burn and creosote is your problem. Vac out the pellet pit prior to every smoke. When I had a Traeger that I was testing I noticed that the burn wasn't always clean. Vac-ing out the pit helped.