Public IP Changes

Take away from that conversation, "PureVPN has a service with their VPN that assigns your connection with a dedicated IP address and port forwarding. It works with PPTP and L2TP / ipsec only but this makes it very easy to set up. PPTP is hardly encrypted and is not standard to use for many VPNs, but it is very very fast and is minimal on latency / bandwidth compromises. 

I use a second router with dd-wrt firmare and use PPTP to connect straight through its WAN connection settings. Super easy to setup, and the dedicated IP you assigned becomes the WAN IP of the second router which means port forwarding is used directly. No need to open any ports or DMZ with the t-mobile router at all. Routers will vary with PPTP WAN support, but this should be a pretty common protocol so others might work the same. 

This is actually easier than it might seem, and it works better than you might expect. The benefit is that you will also have a dedicated IP which is super handy to have. The downside is that there is a cost to these services, but PureVPN also supports OpenVPN so you can use to connect other devices as a standard VPN. Its a work around, but so far its the only way I have found to poke holes through that wall."

Maybe not what you really want to hear but it might just remove frustration from your life.