Some S+G questions, $200's on up and ROI's (Pokerstars)

[OneStuckFish]

3 months after learning what a flush was I started out playing $5.50 sit and goes with an $11.00 transfer from a friend exactly 1 year ago. I forced myself to play at the same level until I had ten buy ins at the next level before I moved up. 1 year later without a single cash out yet, playing 2-3 a day or so, Im at the $200's. My ROI thru the limits were exactly 55% in the 5's, 55% in the 10's, 87% in the 20's (I have no clue what I was doing there), 8% in the 30's (Should have known after that 87% run), 25% in the 50's, 21% in the 100's. In the 50's, and 100's and now in the 200's Ive had some very streaky runs. Cashing in 7 or 8 of 10..then cashing in maybe 3 of 13 or so. Has this proven to be normal? Do the sit and goes get much more difficult above the 200's? Ive found that most of the people I play with in the 200's are the better players from the 100's, and most of them play the 300's and 500's. Should I expect my ROI in the 300's and 500's dip below 20%? Ive have yet to lose my way back into a lower limit using a 10x buy-in rule, but should I consider 20 or 30 before advancing to the 300's or 500's. Is my ROI currently on par with what is considered good, ok, bad or great? I have played exclusively sit and goes for the past year. Given the same bankroll, do you think Sit and goes or multi table tournaments are more profitable? Which has more variance?