Luck,
The definition of addiction I like to use is roughly defined as practicing a behavior and being unable to stop despite significant negative conseqences. Per that definition, sure Poker can be an addiction. $150 + time spent being significantly negative depends on your lifestyle and income. It's a very good sign that you're honest about where you stand.

I would advise you to either stick with ring games or Sit n Gos. Both are significantly different beasts. Personally, I think Sit n Gos are harder because the gameplay changes up A LOT as they progress. However, the bankroll swings aren't as nastly. Also, I don't think being the 3rd or 4rth best player at the table is as rewarding since idiot chips are often burned early (too often to other idiots) and eventually you must take down the sharks and lucky players on tall stacks. However, in a ring game I can avoid marginal situations with strong players and scout out soft games. Granted, this is coming from someone who is an overall loser in Sit n Gos (I've won once and gotten 3rd 3 or 4 times, but I don't play them much.)

Xianti,
Dang man! We need to compare notes sometime...