Double-NAT issue

I have a cable modem (not router) from Cox (Cisco DPQ3212) and I typically run with my own router (Nighthawk 7000). My problem is there is a double-NAT setup that is happening and this is blocking some services (e.g., Back to My Mac).

For example, my router gets an IP (68.111.XXX.XXX) from Cox and on my network it is 192.168.1.1. Doing a traceroute to google.com, I get:

1 192.168.1.1 (192.168.1.1) 0.411 ms 0.254 ms 0.167 ms
2 10.75.151.1 (10.75.151.1) 8.008 ms 6.342 ms 7.663 ms
3 ip68-4-13-176.oc.oc.cox.net (68.4.13.176) 8.648 ms 7.138 ms 7.811 ms
4 ip68-4-11-12.oc.oc.cox.net (68.4.11.12) 8.789 ms 7.540 ms 8.003 ms
5 68.1.1.167 (68.1.1.167) 11.621 ms
...

So, the first is my private network (NAT 1) but the second there of 10.75.151.1 is also a private IP meaning there is a second NAT going on.

If I remove my router and attach a single computer to the cable modem directly I get:
1 6 ms 8 ms 7 ms 10.75.151.1
2 8 ms 8 ms 8 ms ip68-4-13-206.oc.oc.cox.net [68.4.13.206]
3 8 ms 8 ms 8 ms ip68-4-11-20.oc.oc.cox.net [68.4.11.20]
4 11 ms 11 ms 11 ms 68.1.1.63

I hit that same 10.75.151.1 machine. It's either in the Cisco cable modem (doubtful) or some network hardware of Cox's downstream.  (No, it's not something odd on the machine I'm testing with here - have checked on several)

So - how can I avoid the double-NAT?  Any ideas where it's coming from?