I personally would up the amount to about 200-250g. If you're going to sit stirring for the whole roast you may as well make it worth the time. With adding more beans, you can lower the heat of the pan when starting the roast and then you wont over-roast anything that that directly touching. That should bring the colour uniform roast. 9m is a good baseline for roast time. You want to aim for about 1.5-2min for the roast after you hear cracking at an even rate. So you want to heat to bring first crack at 7-7:30minute mark. You won't know how much heat to add until you keep doing more roasts and just trial and error.
The more you roast, its easier to be consistent when aiming for a specific total roast time you aim for. A 9 min roast will be different (but not better or worse) Than a 15min. So just pick a goal and work with that. If you have beans that came out the same colour but one was at 9min and the other at 15, you will find quite a taste difference.
Remember that taste is subjective, and really just try to enjoy the experience as much as your end product.