Most people revise basic maths and physics skills before aptitude testing.
You will know during your PPL phase if your cut out for the job or not....
Do a few lessons with the same instructor, and ask him to be honest, my instructors where to me and where confident I would do well in my commericals....the instructors fly with all types of people, including the people who probably arn't cut out for the job, so I believe there in a better position to say who and whos not than a hand to eye coordination test using a PC.
This is why modular may be better suited, you will get alot of spare change from 60k, plus you have the flexibilities of dropping out, stopping for a break and seeing your wife when ever. Spending 60k on a full time course, and spending max 40k on a modular full time course will get you the same licence, and put you into the same unemployment pool as all the other frozen atpl pilots, plus doing the modular route you will normally have a few more hours to your name.