(1) I believe I read somewhere, either reddit or here, that the phone line port is not meant to be active. It is not an advertised feature of their ‘rural broadband’ Home Internet, so I can’t complain. I too was hopeful I’d get a voice-only line that I could use w/ my home’s existing telephony wiring. I would be willing to pay a small fee extra per month to get even minute-limited VoIP out of this Gray trash can.
(2) There are kits I’ve seen recommended on reddit. But, in that same thread it was disclosed that the advertised kit is not 100% proper for the home gateway. IIRC, the advertised kit was a 2x2 antenna kit, the 5G gateway uses 4x4, supposedly. There *are* antenna connectors inside the unit, but I’d bet T-mo doesn’t like its forum users disclosing the details. I’ve ran across the FCC docs for the unit for the precise bands it uses and power it dissipates using a search engine. (you really are supposed to be taking post-gain calculated power radiated into consideration when buying a high-gain antenna; FCC regs and all that jazz)
The T-mo ISP subreddit should get you going in the right direction, but re-research anything that’s ‘recommended’ to decrease the likelihood of post-purchase headaches or regrets.
FYI, I do not know how large the radius around the registered address’ GPS coordinates that T-Mobile concerns themselves with. There *is* a GPS antenna in the Home Gateway, and there’s always cellular triangulation. They do “reserve the right” to disconnect use in multiple, mobile, or unregistered locations. Not saying you’re doing a No-No; I’d argue you’re not. But more a heads up as to potential overzealous ‘subscriber management’
(3) Over the internet? No, not as far as I know, at least as a simple setup and go deal. (You theoretically could set up a DDNS or remote access to your LAN over the internet some other way to get to the 192.168.12.1 HTTP config interface, over the web) But if you can, or ever will be able to, I guarantee it will be through T-Mobile’s Home Internet mobile application.
(4-5) Currently, as far as I know, no. I do not see any detailed device listings even in the HTTP web interface for the gateway. Some research indicates that the EXTREMELY LIMITED configuration options of the gateway are a well known issue to T-Mobile. Again, should this already be present, or is to be supported, it will probably be through their T-Mobile Home Internet mobile application.
(I will not defend their purposeful and incidental limitations, but I do understand that this isn’t an issue for many expected customers, and is in part cause by a hasteful development and deployment schedule)
(4-5 cont.) It’s also a HUGE spur in the backside of many legitimate (ie, not pushing their limits w/ the Service Agreement) Residential users that happen to actually know what they’re doing with home networking. The best work-around solution I’ve seen thus far (and I’ve implemented myself) is to disable all the WiFi SSIDs manually and ‘disable wifi’ then hook up a decent WiFi router to one of the 2 LAN ports on the gateway. Gateway: LAN1 or LAN2 -> Router: WAN. People do have problems with double NATing, but you might be able to minimize the issue by getting the Gateway to be DHCP server, but the Router merely a configurable access point+switch.
This is not the internet connection for your needs, as stated. Should you ‘make it work’ using a bonding/load-sharing/fail-over service like Speedify; that reliability is on you entirely. I don’t believe most of these VPN datashaping services (that are consumer-facing) offer any uptime guarantees either, and waive any liabilities related in their user agreements. They just advertise ‘reliability’ as a feature that you can configure and enhance with multiple ISPs. Do not expect the level of reliability you need from T-Mobile until they offer a Business-Tier with guaranteed uptimes.