My cooling system was still overflowing out of the reservoir tank and I figured there was one thing that I could do before exploring the possibility of a leaky head gasket. I thought I would replace the thermostat, which would cost me about $10 and some time. Ever since I put in the new thermostat a couple of days ago, my cooling system seems to be stable now. No leaking, and no temperature fluctuations (the engine temp used to drop considerably especially during coasting). I thought the thermostat needed replacing when it stopped the flow of coolant, causing the engine to overheat. Apparently when the stock thermostat failed, it stayed stuck open allowing the engine to run below normal temperatures. I guess I should have paid more attention to my temperature gauge to know where the needle was during normal operation. Now the needle stays in the same place and doesn't hardly move at all.

As far as seeing the bubbles in the system, I figure that might have been residual air in the system. Other than that I can't explain it. Once I put the new thermostat in, I checked for bubbles again and there were none.

Anyway, everything seems fine so far. Thanks again for all the advice. Hopefully this will help someone else someday.