It's hard to gauge where you're really at with anything besides the AAMC CARS passages. Every prep company is offering their interpretation of the CARS section, but it is just an approximation. MCATJelly has been compiling a table of actual MCAT scores and the scores students got on their various practice materials. This might help you to gain some sense of where you're at. With that said, if you're really concerned about where your actual performance is, I'd encourage you to take 6 to 9 AAMC CARS practice passages under timed conditions. Then you'll know what real CARS passages are like and can compare the materials your using to practice with them.
With the two question packs (22 passages each), the two practice tests, and the study guide (5 passages), you have access to 67 AAMC CARS passages. So using 10% of them to find out where you're at isn't going to use up too many of them if you're wanting to save them until the end. (I wouldn't wait until the very end though!)