Change text message forwarding from a device other than iPhone?
Is there any other device I can change text message forwarding option from to make SMS go to my iPad mini?


No.

You need a working iPhone, connected to cellular network and Wi-Fi to enable text message forwarding to your other iOS devices (iPad, iPod touch) or your Mac.

In your current scenario, there is no way to configure SMS forwarding to your iPad mini as your iPhone is not active. Even if SMS forwarding were configured previously on your iPhone, with it not being active, you won't be able to receive the SMS messages on your iPad mini.

However, you can continue to receive and send iMessages with your iPad mini as long as it is connected to Wi-Fi (active Internet connection).

(In case you are not aware, SMS messages can be distinguished from iMessages, by looking at the colour of the message bubble. SMS are shown in green while iMessage are shown in Blue. SMS are sent over your carriers cellular connection and iMessages are sent over the Internet using Apple's servers)

More details can be found in the Apple support article, How to forward SMS/MMS texts on your iPhone.