You do not need a subscription to view away from home. Your ISP or router could be interfering (do you happen to have an Xfinity/Rogers XB7 gateway, known issue with those). Put in a micro SD card if you want to record video without subscription, but not required to view live stream.
Does it work on your iphone when it is connected to home wifi? If so, probably the above. If not, then an issue with the iphone, maybe try reinstalling the app or rebooting the phone?
I would expect it to be warm like anything electronic, but not an alarming amount.
You can turn the camera “off” from the app but that just stops it from detecting motion and saving video or sending video to the cloud, if you want it physically off you’ll want to grab a smart plug (Wyze makes them, many others do too, but using a Wyze one will let you use the same app) and connect it to that, so you can power it completely off and on remotely.
NOTE - do not uninstall the app if you are still on the 2.X version. That likely means your device is not compatible with 3.x and you can no longer do a new install of 2.X!!