Google message app unusable

My Google message app has been slowing down over the past few months and now I need to close the app every time I want to read a message. I then can't do anything else with the app unless I close it again. I have tried the following:

Rebooted phone

Cleared app cache

Cleared phone cache

Factory rest phone (with out losing data)

I have change the app to the beta version to download a different version. 

I have messages from Mom (who is gone) that I don't want to lose. 

I haven't uninstalled and reinstalled the app yet 

I have 1.7gb of messages on the phone. 

Is there anything else to do?

Thanks