Hello!
Your phone COULD be 'timing out' the cellular data connection to save power. On MY phone, I have to use an app called Battery Booster to set the phone to 'Basic Saving Mode'. This keeps the data connection alive.
I have a similar phone (BLU Advance 4.0), and I tether (and hotspot!) on it using LL from time to time without issues - even on Net10.
NB: On Net10/StraightTalk phones bought from retail outlets, these features are disabled in the ROM by the carrier - another reason to Bring Your Own Phone to Net10, StraightTalk, etc.
On the phone, I have USB debugging enabled, disable WiFi, go to System Settings > More (under Data Usage) > Tethering & Portable Hotspot, and check 'USB tethering'. In LL on MY PCs, this shows up as 'Wired Connection 1'.
Since Linux and Android use the same default TTL (time-to-live) for IP packets (64ms), it shouldn't be giving you a problem. In this case, cellular carriers can't tell whether you're on the PC or on the phone, since the IP packets share the same TTL.
Another little tidbit: if you change your default TTL in Windows from 128ms to 64ms, you can ALSO tether to a Windows PC with an Android phone. Google it to see exactly how, but it involves adding a registry entry to specify the DefaultTTL to be 64ms on the Windows box. Again, they think you're on the phone.
I wouldn't be caught dead owning one, but I imagine this would also work on a FruitPhone (iPhone) but setting the default TTL to that of a FruitPhone, but not sure how to do that in Linux...
73 DE N4RPS
Rob