One possible thing you might want to look into is Anycasting your DNS servers, although understandably this is costly. I myself was researching starting a DNS p

One possible thing you might want to look into is Anycasting your DNS servers, although understandably this is costly. I myself was researching starting a DNS provider after Dyn bought EveryDNS, however the inability for me to find a way to cost-effectively provide Anycast was what stopped me in my tracks. What you have right now looks good, good luck.