How do you know the SD card is not working, if you go to storage does it not show up?
The applications you are using should have an option to save to the SD card, like your camera app.
The SD card is slower than the internal storage of the phone but it won't be slower enough that you would notice when getting files from it.
For the backup, turn on Google cloud and it will automatically save things to your Google account in Photos. Verizon is probably backing up your text message already, go through the options of the phone Verizon apps and you can also just contact Verizon support or do a web search.