Something that you could try which I've done:
Take your Ooma Telo to a friend or relative's home that has faster Internet speeds. At your friend or relative's home, you can check and see if you experience any differences in call performance without any costs to you, except time.
One of the setups I did was put the Ooma after my router on port 8, then set my router with port 8 to "high" with 1-7 to "low". That was better than it was in front of the router but still had glitches. With this same configuration I then set my upload to 500k on the router with the same results, better than in front of it but still choppy and I could clearly see my upload speeds being limited by the router.
I would find it very hard to believe my upload is ever actually below 500k but there could be something else going on with Time Warner and that wouldn't surprise me at all.
I also haven't tried a full re-boot of the Ooma which I should, that may fix the QoS glitch as well but with it working great right now I don't want to mess with it and get my wife upset again