Welcome! It's always great to have another pro join in, especially here where there is such a small number of them active. Most of us are just shade tree guys who look to these forums to get as much information as we can before starting on repairs that are typically going to be first-time jobs.
I've done 3 timing belts, and have always used an inch torque wrench on those WP Allen bolts. I believe that the combination of squishing the O ring, along with the sideways torque from the timing belt, makes finding the correct tightness fairly problematic. Maybe someone who has done lots of these can do it accurately by feel, but I wouldn't feel comfortable without the TW, especially consdering how important it is to get these bolts done correctly.
I too would be interested to know what you like about the Aveo. I've always thought of it as a decent, low-end vehicle. My '05 has been a great daily driver for me for 9 years, and also an '06 has done well for my daughter. But I've never considered it to be above average in any way, so I would be interested to read your professional opinion about it.