Hi Matheus!
I’m working in the exact same thing!
I recommend you to use the ROS package developed by patrick here.
I have a fork of this same package that I use in python 3.6 with ROS melodic (here). I have to say that my package is prepared for my personal preferences and my configuration in the ROV, but maybe you’ll find it useful. The changes required for this python and ROS version are not huge though.
The node already reads the camera and IMU data. Only the barometer is not directly included. With the help of patrick (see this topic) I made my own node to read the barometer, you can find it here. (In the develop branch I’m developing some further functionalities for the node, in case it is of your interest).
Hope it helps. 
Let me know if you make some progress of your own! 